In view of the long dissolution time of polymer used in offshore platform oil displacement, the large volume of injection system and the contradiction with the load-bearing and limited space of offshore platform, a polymer grading forced stretching device for offshore platform is designed. Through the relative movement of the two-stage instant ring, the swelling layer on the surface of the polymer swelling particles is stripped, and the internal non swelling part is in rapid contact with water, so as to increase the specific surface area in contact with water and improve the two-way penetration rate of water polymerization, so as to shorten the polymer dissolution time. The fluid flow law and pressure distribution in the device are studied by fluent numerical simulation. In a single flow passage, the closer to the wall, the greater the velocity vector, the stronger the shear stress and the stronger the transverse tensile effect on the polymer swelling particles;At the movable gap between the lower fixed teeth and the moving teeth, the static pressure loss is the highest, and the dynamic pressure of the device reaches the maximum. The polymer swelling particles are forcibly stretched to accelerate the dissolution of the polymer. The field test results show that the basic dissolution time of polymer APP4 is shortened from 80 min to about 40 min, and the viscosity retention rate is more than 90% . The viscosity of the solution is almost the same when it is basically dissolved.