Bohai LD Oilfield is developed by commingling production in thick layers. Due to the field test at early polymer injection and the effect of gravity on developing the thick reservoirs，the remaining oil in the period of middle and high water cut is relatively complicated. In order to further study the remaining oil distribution of oil reservoir after the polymer flooding，laboratory core displacement experiment was carried out. Combined with the reservoir properties，physical simulation parameters were designed according to the similarity principle，and the effect of different stratum rhythm on remaining oil distribution in the early polymer injection and the production performance was researched. The research results indicate that due to gravitational differentiation，the oil reservoir is flooded at the bottom under the condition of homogeneous rhythm，and early polymer injection can slow the gravitational differentiation to a certain extent，so the remaining oil is mainly concentrated at the top of the reservoir near the production well；under the condition of positive rhythm，influenced by the gravitational differentiation and the reservoir heterogeneity，the high permeability layer is flooded at the bottom and the remaining oil is concentrated in the lower permeability layer at the top；early polymer injection can effectively drive the remaining oil in the medium and low permeability layer，and the remaining oil is concentrated in the low permeability layer near the production well；under the condition of reverse rhythm，the swept degree of water flooding is relatively uniform，and the remaining oil is mainly concentrated in the locally non-swept region，and the early polymer injection can further extend the swept degree；under the condition of composite rhythm，the displacement situation of water drive and the polymer drive are similar to that of the homogenous rhythm，and the remaining oil is concentrated in the low permeability layer near the production well.