Abstract: In view of choicing equilibrant reasonably, the stress concentration of drive shaft caused by the equilibrant can be effectively reduced. Taking the rough rolling mill (R2 rolling mill) of a Steel Plant as the research object, a model of main drive shaft device of R2 rolling mill was established according to the size of each component of the device. The mechanical analysis of the components was carried out, the equilibrium equation was established, and the formula relationship between the equilibrant of drive shaft of R2 mill and the driving force of hydraulic cylinder was derived. The theoretical solution of equilibrant of drive shaft was calculated by means of MATLAB programming. The three-dimensional model of main drive device of the rolling mill was introduced into ADAMS software, and the simulation solution of equilibrant of drive shaft was obtained, it was compared with the theoretical solution. The results show within the range of working angle of main drive shaft of the rolling mill, under the same inclination angle, the deviation between the theoretical solution and the simulation solution of equilibrant of main drive shaft is small, which can be ignored. The reliability of the derived formula relationship is verified, and the research results are of guiding significance for the selection of hydraulic cylinder driving force.