止損單是交易者設置的自動下單或平倉的指令——當價格位於特定的價位，買或賣的指令即被下達。交易者所遵循的首要交易紀律是：限制損失。止損單就是為了方便交易者限制潛在的損失，設置在多單的下部和空單的上部。
例：如果你在$90.00買入1，000股IBM股票，你可以在以下位置設置止損：
當IBM股價低於或等於$87.00時，將手中的1，000股平倉。
如果價格達到 $87.00，那麼你的止損指令將會被觸發。
加上佣金，你每股的損失被限定在$3.00。
通常，市場缺乏流通量時會導致極端的價格波動，應該避免在這種情況下交易。
止損單的種類
• 市價止損單（Market Stop Orders）
是一種常見的止損指令，指的是一種當市場價格達到某一特定水平時買進或賣出的指令來減少自己的虧損。
• 限價止損單（Limit Stop Orders）
止損限價單指令系統在用戶指定的止損觸發價格被觸碰或超越時提交一份買或賣限價單。
• 固定價止損單（Fixed Price Stop Orders）
定價止損是當價格達到某一水平時觸發止損。一些交易所稱它為限價止損，因此在交易前要確認所採取的止損種類。
在入場之前，推薦使用限價止損單：與定價止損單相比，限價止損單被執行的可能性更大。並且限價止損單沒有市價止損單的開放性（不論市價是多少，你的單子都將被執行）。
平倉時建立採用市價止損單：保證你的單子盡可能地以最優價位執行。如果價位迅速下跌，不要抱著價格將會反轉的希望，而是應該需立即平倉。埃德溫•勒菲弗在股票作手回憶錄中總結了一個困境：“他們開始時不願意承擔一個小小的損失，而是繼續持倉，並希望在收支相抵時出場。然而，價格卻在接連不斷的下跌，損失也越來越大。似乎唯有繼續持倉才是正確的選擇，因為價格在一年左右肯定會回到該價位。隨著價格持續走低，越來越多的人抛售，最終，不管他們願意與否，都會被市場強制出局”。
止損指令的評價
止損指令並不總是完美執行。如果一個主要的支撐位被打破，大量的止損單會在同一時間被觸發。賣方遠比買方多，導致價格猛跌，導致賣出指令不能被執行。極端情況下，甚至會沒有買方的出現。
盡管止損指令不完美，但確能有效的將損失限定在一定範圍内，並保護資產的流失。如果所交易的市場中沒有止損，那麼設置自己限價單並從經紀商訂制短信提醒服務。另外，止損需要毫不猶豫的自律性。
所需的步驟
1.首先，確定你可接受的最大損失;
2.基於良好的技術水平設置止損水平;
3.不斷的調整你的止損水平，鎖定利潤;
4.使用跟蹤止損來確定進出市場的時間。
Stop Loss Orders
Stop loss orders ("stops") are limits set by traders at which they will automatically enter or exit trades - an order to buy or sell is placed in the market if price reaches a specified limit.
The first discipline that any trader should master is to always limit your losses.
A stop loss order is set to limit a trader's potential loss. The stop loss is placed below the current price (to protect a long position) or above the current price (to protect a short position).
Example: If you purchase 1,000 IBM at $90.00 you may decide to place a stop loss as follows:
SELL 1,000 IBM IF price is less than or equal to $87.00
If price falls to $87.00 your order will be activated.
Your loss is limited to $3.00 per share (plus brokerage).
As a rule: avoid markets with low liquidity where extreme price fluctuations are possible.
Stop Loss Order Types
• Market Stop Orders
This is a conventional stop loss order - the stop activates a market order to sell (or buy) at the prevailing market price.
• Limit Stop Orders
The limit stop activates an order to sell at the prevailing market price but not below a specified limit (or buy at the prevailing price up to a specified limit).
• Fixed Price Stop Orders
The stop loss activates an order at a fixed price. Some exchanges refer to these as limit stop orders so check that you are using the correct stop loss order.
Limit stop orders are recommended for entering a trade: they have a greater chance of success than fixed price orders but are not as open-ended as market orders (where your order will be executed no matter what the market price is).
Market stop orders should be used to exit trades: to ensure that the order has the best possible chance of execution. Never hold on to securities if price falls sharply - in the hope that they will recover. Edwin Lefevre sums up the predicament in Reminiscences of a Stock Operator :
It was the same with all. They would not take a small loss at first but had held on, in the hope of a recovery that would "let them out even." And prices had sunk and sunk until the loss was so great it seemed only proper to hold on, if need be a year, for sooner or later prices must come back. But the break "shook them out," and prices just went so much lower because so many people had to sell, whether they would or not.
Evaluation of Stop Losses
Stop loss orders do not always work perfectly. If a major support level is breached, a large number of stops may be activated at the same time. Sellers will far exceed buyers, causing price to fall sharply and leaving sell orders unfilled. In extreme cases there may be no buyers at all for a security -- not at any price.
Imperfect as they are, stops are still an effective mechanism for limiting risk and protecting capital.
If stops are not accepted in a market, set your own limits and place buy or sell orders when the price is reached. Use SMS alerts if they are available from an online broker. Self-discipline is required to execute stops without hesitation.
Steps Required
1. First, determine your maximum acceptable loss;
2. Set stop loss order levels based on sound technical levels;
3. Adjust your stop loss levels over time to lock in profits;
4. Use trailing stops to time your entry and exit from the market.
本文翻譯由兄弟財經提供
文章來源：http://www.incrediblecharts.com/trading/stop_loss_orders.php