Considering the specific behavior of indirect measurement of flow rate in the polymer extrusion process，a quasi-static digital filtering method，intermediate between dynamic and static measurements，was proposed.By means of this method a direct measurement of the dynamic variables was transferred into an indirect measurement of static variables which demonstrated relative stability in comparison with dynamic variables.Based on this concept，the influences of stochastic and periodic disturbances in extrusion process on measurement accuracy of flow rate were eliminated effectively by using limit filtering and recursive-average filtering.The optimal filtering parameters，including sampling time T and recursive number N，were determined by experiment.Experimental results showed that the output value of quasi-static digital filtering fitted with the actual value very well.