[QUOTE=ChrisW67;259988]So your project has a resource file called "something.qrc" with entries like
Qt Code: 
  1. <RCC>
  2.     <qresource prefix="/">
  3.         <file>plot/image/run.png</file>
  4.     </qresource>
  5. </RCC>
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And you have opened and used a file called ":/plot/image.run.png" (Note the colon ":" in the path) from the resources not the local file system.

OK, I got it. The problem is not in the resource file. The problem is in the .ui file. From your tips, I went to look at the .ui file. I found the .png file has the </normaloff> header. Although I did not put in it when I specified the "icon" (I did not specify anything under sub-icon), ui properties put .png under "normal off" sub-icon. I delete .png from "normal off" up and put it in "normal on" sub-icon. It wokrs now. Thanks!!!