To obtain the global convergence in the sequence quadratic programming(SQP) method, one often uses a penalty function.Due to its non-differentiability, the general penalty function will cause some numerical difficulty.The Lagrange function can overcome this difficulty, but it is complex in form.In the paper, a kind of smoothing penalty functions was developed and a sequence quadratic programming algorithm for equality constrained optimization problems was proposed.The smoothing function is based on the cosh function and it is continous, diffientiable and convex.The global convergence was achieved under certain conditions.The numerical tests were also given to show the effectiveness of the proposed algorithm.