When I the connect the output voltage of regulater 5V to pic , the voltage drop to half , why?
TTU.ABD:
When I the connect the output voltage of regulater 5V to pic , the voltage drop to half , why?
Go ask the pic people, arduinos don't do that. 
If the regulator gets real hot at the same time, then it is overloaded and folding back the voltage. Otherwise, if you don't have the appropriate capacitors on the input and output, it could be oscillating.
Are these the actual measured voltages?
Does the LED pass enough current for the regulator to work?
OP's schematic showed up in a belated fashion. Someone tell him how to measure voltages.