In order to solve the problems of high labor intensity and easy falling when climbing the tower crane, a pure intelligent safety climbing aid with high reliability and easy installation is designed and developed, which includes drive device, hydraulic buffer device and wire rope. For the design of the drive system of the climbing aid, the traditional method is not the best optimization method because it is easy to get the local optimal solution. Aiming at the deficiency of traditional methods in multi-objective optimization, this paper proposes to use genetic algorithm to optimize the transmission system of climbing aid mechanism. The evolutionary process is simulated by genetic algorithm. This study takes the design of a conical cylindrical gear three stage gear transmission system as an example, with the optimization objectives of structural compactness and equal strength of all levels of transmission, and proposes a spatial layout optimization plan for the gear transmission system based on NSGA-II genetic algorithm. Compared with traditional design methods, the total volume of the gear transmission system has been reduced by 30.62%, while ensuring that the transmission strength at all levels is basically equal, improving the structural compactness and load-bearing capacity of the gear transmission system, and verifying the effectiveness of the spatial layout design method of the gear transmission system proposed in this article.