I use renderman rendered a tiff file and its z-channle .zfile,and how can
I make a depth of field effect in a compositing software, such as shake,
Digital Fusion??

Greate thx.

You'd probably be better off asking in a DF or Shake forum if you want to use those apps specificly, but you can do it in Halo or Houdini's compositor.

Take a look at the ZDepth compositing and Depth of Field videos on this page:

http://www.vislab.usyd.edu.au/sidefx/houdini_video/by_topic/compositing/index.html [vislab.usyd.edu.au]