A new improved Strongly Implicit Procedure is presented for solving the large sets of equations with matrix of coefficients A in fluid mechanics.This algorithm has several advantages over those now in use.First,auxiliary matrix à is symmetric and matrix A+à is positive definite and symmetric matrix when A is symmetric.This ensures the numerical stability of the iterative algorithms.Second,for an appropriate choice of iterative parameter ω,the rate of convergence of the new iterative procedure should be faster than original SIP scheme.Numerical results of two dimensional flows are given with the scheme. It is shown that the algorithm is very efficient.