For bistable electromagnetic reversing mechanism in hydraulic directional valve,the calculation is complicated when empirical method is used to calculate permanent magnet and the structure is checked by iteration.To overcome the problem,a global optimization model was deduced by using magnetic circuit method and the simulation verification was conducted by using Maxwell.Constraint condition was put forward based on engineering practice, the fmincon function module in MATLAB was used to solve the ideal results.The optimization model makes the design objective more clear and the calculation process more concise, which improves the design efficiency to some extent.