Abstract: Two kinds of wholly aromatic thermotropic liquid crystalline copolyesters (LCP) based on HO- - -OH or HO- -CH₂- -OH were prepared, then blended with polysulfone for preparing in-situ composites. The variations on torque of blends in melt process have been studied. And effects of chain structure, molecular weight and content of LCP on rheology of in-situ composites have been investigated. It is obtained from the curves of milting flow that the melts of in-sits composites for polysulfone conform to non-Newton's law of viscosity and showed pseudolasticity. The morphology and compatibility of LCP and polysulfone have been also discussed.