Aiming at reducing the maximum thrust of the cylinder and improving the smoothness of the luffing action of the straight-arm aerial working platform, firstly, the working principle of the amplitude changing mechanism and the mathematical modeling of the cylinder thrust were analyzed, and the accuracy of the mathematical model was verified through tests, then, the design variables, constraints and objective function expressions of the optimization problem are determined on the basis. NSGA-Ⅱ( fast non-dominated sorting genetic algorithm) was used to solve the multi-objective optimization problem, and Pareto front optimal solution set was obtained. The comprehensive satisfaction function based on signal-to-noise ratio was used to evaluate the solution set, and the solution with the highest satisfaction was selected. Finally, by comparing the results before and after optimization, it can be seen that the optimal design based on the high-precision mathematical model reduces the maximum thrust of the luffing cylinder by 10.8%, the maximum displacement change rate of the cylinder for each 1° of luffing decreases by 28.4%, and the cylinder stroke goes down by 2.1%.