I don't think so. search by file size seems like search by date,isn't it?
I find a way to resolve my problem. (xpath)
for example: (0~100K)
/jcr:root/okm:root//*[@jcr:primaryType eq 'okm:document' and @okm:content/okm:size>0 and @okm:content/okm:size<102400 ] /(@okm:author|@jcr:created)