对于 .Net <= 4.0，请使用TimeSpan类。

TimeSpan t = TimeSpan.FromSeconds( secs );

string answer = string.Format("{0:D2}h:{1:D2}m:{2:D2}s:{3:D3}ms", 
                t.Hours, 
                t.Minutes, 
                t.Seconds, 
                t.Milliseconds);

（如Inder Kumar Rathore所述）对于 .NET > 4.0，您可以使用

TimeSpan time = TimeSpan.FromSeconds(seconds);

//here backslash is must to tell that colon is
//not the part of format, it just a character that we want in output
string str = time .ToString(@"hh\:mm\:ss\:fff");

（摘自Nick Molyneux）确保秒数小于TimeSpan.MaxValue.TotalSeconds避免发生异常的时间。