Abstract: The two difficulties such as injected polymer molecular weight optimization and fine multiparameter reservoir evaluation have become the key problems to be solved urgently in the process of polymer flooding. Taking the conglomerate reservoir of the lower Karamay formation in District Qidong-1 of Karamay oilfield as the study object, the paper uses physical simulation methods to identify the relationship between recovery factor and polymer molecular weight, that is, the recovery factor will decrease gradually after the polymer molecular weight reaches 1 500×104. Based on which, taking the radial amplitude difference between of compensated density log and neutron porosity log as a regressive parameter, a model is established to calculate shale content. The permeability model established by using porosity and shale content can evaluate the seepage property of the conglomerate reservoir more accurately. Based on the results of physical simulation experiments and reservoir multiparameter interpretation, the optimal injected polymer molecular weights in different subregions are determined for the conglomerate reservoir of the lower Karamay formation in District Qidong-1, good application effects have been gained and the daily oil production has been improved from 149.2 t to 515.8 t after the implementation of polymer flooding program in the study area