Typhoons and heavy rain are the main causes of the flood disaster in Zhejiang island areas. Petrochemical bases in island enclosures have special requirements and characteristics on the site pattern，drainage water level，and drainage water quality. Taking the Zhoushan petrochemical base as a research object，this paper establishes the one-dimensional hydrodynamic model in the study area which combined with island region typhoon rainstorm characteristics，petrochemical base site layout requirements，and drainage conditions. Not exceeding the river target level of the river is the control requirment. Through the simulation analysis of different working conditions，a better drainage system and engineering scale are determined to ensure the safety of petrochemical base drainage.