On the basis of dynamic criterion for free electrons, a traditional averaged atomic model (AAM 1) is improved in several aspects. The continuum radial wave function in central field approximation is normalized in a certain boundary condition. The contributions of the free electrons are dealt with in four parts to improve the precision of electron pressure. The condition of normal density is spontaneously satisfied. As samples electron pressure of Iron, Nickel, Lead and Americium are calculated and compared with the results other theories and experiments.