Abstract: Flexible spacer, (n=4, 6, 10, abbreviated to C_(4-s), C_(6-s), C_(10-s) respectively) was inserted into the polymer chains of a series aromatic copolyesters obtained from chlorohydroquinone (HQCL) and non-linear biphenol: 4, 4'-sulfonyldiphenol(SDP) or 4,4'-isopropylidenediphenol(BPA). The effect of nonlinear unit of biphenol and flexible spacer on liquid crystal properties of these copolyesters was studied by inherent viscosity, DSC and hot-stage polarized microscopy. The results show that these copolyesters have the typical texture for the nematic state and the maximum mole content of the nonlinear biphenol in these copolyesters without destruction of their liquid crystal properties will increase when the polymer chains hold flexible spacer. It was found that the maximum mole content of SDP in copolyester C_(4-s)/SDP/HQCL was 55%, BPA in C_(4-s)/BPA/HQCL and C_(6-s)/BPA/HQCL was 40%, and in C_(10-s)/BPA/HQCL was 50%.