Application of hot stamping technology of advanced high strength steel is one of the effective approaches for automotive light-weighting. It is important to investigate the effects of hot stamping process parameters on forming quality for the application of hot stamping technology. A kind of hot stamping tool system for process tests of U-shape sample is introduced. It includes cooling system and temperature measuring system and it employs springs to provide blank holder forces. The effects of process parameters, blank holder force, cooling rate, initial temperature of blank, stamping velocity and die unloading temperature of blank, on the dimensional accuracy and microstructure of hot stamping samples can be investigated on the hot stamping tool system. Satisfied hot stamping U-shape samples were obtained by optimizing the process parameters.