Abstarct: In this paper, we investigate a series of successive and repetitive processes that lead to the best approximation. We introduce this process remez algorithm. Expressing approximation theorem, obtains approximation of a funection f in C[a,b] in set of polynomials is a polynomial of degree most n and show existence and uniqueness of the best approximation. Finally by remez algorithm computing best spline function approximation of degree n with k fixed knots.