Polymer microsphere is a deep profile control agent which has been developed in recent years. Microsphere’s excellently elastic property makes it possible to be injected, or to penetrate deep into formation, and plug high permeable layers. Many laboratory investigations have been carried out on polymer microspheres by researchers, and field tests also have been done in some oilfields. The laboratory and field test results show that polymer microspheres can plug pore throats effectively, decrease permeability of high permeable channels, thus force injected water to change it’s direction and enhance water-flood sweep efficiency. In this paper, based on the mechanisms of profile modifying and plugging of polymer microsphere, Streamline models have been build abstractly to simulate the profile controlling progress of polymer microspheres, observe the transformation of streamline field, and analyze its impact on the pressure of water injection wells and performance of oil wells. In the end, the mechanisms of profile modifying and plugging of polymer microspheres have been interpreted based on the streamline field.