Abstract: Based on the offshore oil field reservoir characteristics, screening clay anti-swelling agent has very important significance to control damage of reservoir water-sensitive and ensure the sustainable and efficient development of entire field. Comprehensive considering the advantages of various evaluation methods of anti-swelling agents, this experiment combined static and dynamic experimental evaluation method to screen water injection clay anti-swelling agent for an offshore oil field. For the optimized FP-3A clay anti-swelling agent with the mass percentage of l%, the anti- swelling rate of static-evaluation centrifugal method is 79.1%, 54.6% by X-ray diffraction method, 80.7% by anti-swelling dilatometer method, core linear expansion rate is 0.73%, the amount of 0.29 g per 100 g static-adsorption. The retention rate of dynamic permeability is greater than 94.74%, the best injection concentration is 0.5% to 1.0%, and the penetration rate fluctuation is small, anti-swelling effect is stable and the acting time is long, it is suitable for the development of offshore oil field.