In order to simulate heterogeneous reservoir, six parallel homogeneous cores are used to conduct laboratory experiments of polymer flooding after water drive and the indexes of shunt rate, water cut and recovery factor are compared under different alternating injection cycle of polymer flooding stages. The results show that, when the alternating injection cycle is 0.2PV, it can better restrain profile reversal in the process of polymer injection displacement and make profile reversal appear later. Meanwhile it can improve the sucking fluid proportion of low-permeability layer and make overall water cut stay at low point much longer and then get higher recovery factor.