A photo-isomerization of azobenzene and its opto-mechanical effect on the photoactive liquid crystalline polymer is investigated via molecular dynamics (MD) simulation. In order to describe the cis-state of the azobenezene in classical MD model, an additional dihedral potential parameter of N=N bond is implemented into the fully condensated nematic polymer model. During the photo switching simulation, both the local conformational changes in the mesogen-contained microstate and the global photostrain of the bulk system are observed successfully with respect to the isomerization ratio in the molecular unit cell. For each relaxed model under photo-activated condition, a heating-up simulation is carried out sequentially, and the effective deformation of the material is characterized as a function of both temperature and isomerization ratio of the photoactive mesogen.