This theory has important applications of polynomial approximation in various areas of functional analysis, Fourier analysis, application mathematic, operator theory, in the field generalized derivatives and numerical solutions of differential and integral equations, etc. The study of approximation theory is a well-established area of research which deals with the problem of approximating a function f by means of a sequence n L of positive linear operators. This theory is very important for mathematical world. Nowadays, many mathematicians are working in this field.