執行緒優先順序從高到低分為：Highest 、AboveNormal、Normal、BelowNormal、Lowest共5個等級。通過設定Thread類的ThreadPriority屬性（可讀寫屬性）來調整。

範例：

下面的程式碼示例說明了更改執行緒優先順序的結果。建立兩個執行緒，其中一個執行緒的優先順序設定為 BelowNormal。兩個執行緒在 while 迴圈中都增加一個變數，並執行一段設定的時間。

using System;

using System.Threading;

class Test

{

static void Main()

{

PriorityTest priorityTest = new

ThreadStart startDelegate =

new ThreadStart(priorityTest.ThreadMethod);

Thread threadOne = new Thread(startDelegate);

threadOne.Name = "ThreadOne";//通過設定執行緒的name加以區分。

Thread threadTwo = new Thread(startDelegate);

threadTwo.Name = "ThreadTwo";

threadTwo.Priority = ThreadPriority.BelowNormal;

threadOne.Start();

threadTwo.Start();

// Allow counting for 10 seconds.

Thread.Sleep(10000);

priorityTest.LoopSwitch = false;

Console.ReadLine();

}

}

class PriorityTest

{

bool loopSwitch;

public PriorityTest()

{

loopSwitch = true;

}

public bool LoopSwitch

{

set { loopSwitch = value; }

}

public void ThreadMethod()

{

long threadCount = 0;

while (loopSwitch)

{

threadCount++;

}

Console.WriteLine("{0} with {1,11} priority " +

"has a count = {2,13}", Thread.CurrentThread.Name,

Thread.CurrentThread.Priority.ToString(),

threadCount.ToString("N0"));

}

}

執行結果：很明顯，高優先順序的執行緒擁有更多的執行機會。