  The relationship between the parton transverse momentum and longitudinal
momentum, which is obtained by analysing the hadron tensor in the deep
inelastic scattering (DIS) process, indicates that the transverse size of
partons in a nucleon is sensitively affected by the effective nucleon mass. The
change in this transverse size gives rise to an Additional Parton Evolution
(APE) in the nuclear environment refer to the normal QCD parton evolution thus
resulting in new parton distributions. The self-consistent integral equations
for these new parton distributions are given. Having undergone the normal QCD
evolution and the additional evolution in the nuclear environment, the partons
with the small x participate in recombination and contribute to the nuclear
shadowing effect. The reasonably good descriptions of the nuclear effect of
structure functions, nuclear Drell-Yan ratios and nuclear gluon distributions
are presented. A quantitative comparison between the APE model and the
Q^2-rescaling model is made.
