A series of novel thermotropic side-chain liquid crystalline polymer based on polymethacrylate backbone containing electron-accepting 4-(4′-nitrophenylazo)phenoxy as nonlinear optical active group and electrondonating 4(4′-methoxyphenyl) phenoxy group as mesogen attached covalently to the backbone through the flexible spacer was prepared and characterized, respectively. The results from differential scanning calorimetry showed that these series of copolymers were enantiotropic liquid crystal with single mesophase. The melting points and the relative enthalpy change of the copolymers depressed with increasing the molar percent of 4′-nitroazobenzene monomer units over 0∼50mol%, but the enthalpies change of the transition from mesophase to isotropic state increased for the copolymers containing 0∼50mol% 4′-nitroazobenzene units. The texture observed under polarized optical microscope identified that the copolymers containing 24molar% or more than 24mol% 4-nitroazobenzene monomer units could form smectic mesophase with the focal-conic texture. The results detected by WAXD were in good agreement with the results observed by POM.