Side chain liquid crystalline polyesters (PMx) were synthesized through the melt polymerization between N-6-(4-((4＇-nitrophenyl)azo) phenyl)oxy)hexyl diethanolamine (C6), maleic anhydride and succinic anhydride. The effect of the polymer backbone on the phase behavior of PMx was studied by DSC, polarized optical microscopy (POM) and wide angle X-ray diffraction (WAXD) and the results showed that smectic -isotropic transition temperature (T-SI) increased largely, while melting temperatures (Tm) decreased slightly and Tg increased slightly with the increase of the content of maleic anhydride in the copolymers. The results also indicated that introduction of maleic anhydride to polymer backbone was unfavorite of the molten crystallization of the side chains. The IR-dichroism study on the side chain liquid crystalline elastomers prepared from PMx showed that the elastomers exhibited anisotropic behavior after stretching under the mechanical fields.