Using the variational method, influence of the amplifier spontaneous emission (ASE) noise upon the optical pulse in dispersion management system is discussed, thus, the pulse phase variance, central time variance and center frequency variation with distance are obtained. And influence of the ASE noise is discussed in the densely dispersion managed soliton system and the larger negative average dispersion. The numerical simulation results show that the densely dispersion managed soliton system and the larger negative average dispersion can reduce the pulse impact of ASE noise.