Dear sir,
My name is umer iqbal am I blacklist for uae.I already travel uae on visit visa.. but now he told me blacklist.not giving employement visa.. what is this.. please ans me

Okay, phrase it another way. You are BLACKLISTED so you can't get a visa to work.

Ok.
But I don't know reason of blacklisted.. I am not involved any crime or any other bad activities.so why that.?
What's the issue in uae law. I think same name problem or mistake..? How I can check.. so please guide me?

Did you leave before a contract was over, did you leave with any unpaid debts or loans? There can be a number of things... not just crimes.