The geometric parameters are optimized at the B3LYP and CI levels under the constraints of the C2v, C2v and C2h symmetry point groups for the three isomers of dichloroethylene. The theoretical two-dimensional electron momentum distributions and momentum profiles of four core orbitals for iso-dichloroethylene, cis-dichloroethylene and trans-dichloroethylene are calculated by non-relativistic density functional method. Comparing the electron distributions in position and momentum space of these orbitals, it is found that the interference effects, which do not exit in position space, appear and produce the evident periodical multipeaked momentum distributions in momentum space. The distances between atoms and the alignments of molecular axes for these three isomers can be obtained by computing their values of period and the axis directions of period, respectively.