In this paper, we examine the computational limitation 
of low degree polynomials over finite fields. We 
prove that no o(log n)-degree polynomial 
of n variables over Z_q
can compute the modulo function MOD_m over Z_q^n,
where q is a prime and m is coprime to q.
Our main technical contribution is to estimate a correlation 
between low degree polynomials and modulo functions 
over prime field Z_q by computing 
the Gowers uniformity of exponential functions,
which generalizes Viola and Wigderson's estimation over Z_2.