Can i use 8 gauge wire with 10 gauge ground with double 50 amp breaker
You can't use #8 on a 50A circuit

You have to read out of the 60C column of 310.15(B)(16), which means you are limited to 40A.  

It would be possible with other classes of wire in conduit,  but not possible with the usual types of cable used in America used for this job (which is what you are referring to). 

If you really need 50A, then change to #6 cable.  

But the ground is fine

Circuits up to 60A are able to use a 10 AWG ground. 

The conductors need to carry current continuously.  The ground only needs to carry current long enough to trip the breaker.