In order to study the hydroforming regulation of longitudinal beam of car and provide the necessary guidance for its engineering application, the experiment and numerical simulation of the pulsating hydroforming rectangular tube were carried out，and the correctness of simulation was verified by experiment. Then, the hydroforming process and main parameters of the longitudinal beam were confirmed, and the whole process of forming was simulated. Based on the above facts, the influences of hydraulic loading path and friction coefficient  of contact surface between die and tube on the wall thickness distribution and the maximum thinning rate of the longitudinal beam in hydroforming were analyzed. The results show that in conventional loading the pressure is increased to approximately half of the forming pressure in the early stage, maintained for a period of time, and then increased to the forming pressure in the later period. In this loading path,the maximum thinning rate is the smallest, and the wall thickness distribution is the most uniform. Based on the above loading path, the pulsating hydroforming loading path can further improve the quality of longitudinal beam. At the same time，the smaller the friction coefficient is，the smaller the maximum thinning rate of forming is，the closer the wall thickness to that of initial tube is,and the more uniform the wall thickness distribution is.