The rheological properties of the sludge in the wastewater treatment plant were analyzed, and the changes of the rheological characteristics such as limit viscosity, yield stress and thixotropy of sludge with different TS were investigated. The effects of TS and temperature on sludge rheology characteristics were discussed. The results indicated that when the active sludge TS is 0.86% showed the characteristics of pseudoplastic fluid as the shear rate increased from 0 to 100 s-1, but showed the characteristics of the expanded plastic fluid with the increasing shear rate(from 100 s-1 to t1000 s-1). The variable properties can be described by the Herschel-Bulkley model; the yield stress is in the power-law relation with TS; the limiting viscosity and the area of the thixotropic ring are exponentially related to the TS; the sludge viscosity and the area of the thixotropic ring decreased with increasing temperature. And the changes in viscosity were more obvious at low shear rate, but it was not significant at high shear rate.