The press hardening steel (PHS) and hot-stamping components were utilized widely on the reinforcement and lightweight structure of car body due to its ultra-high strength. There existed an obstacle of hydrogen embrittlement (HE) for coated 1.5-2.0 GPa PHS, and uncoated 1.8-2.0 GPa PHS. The typical hot-stamping components were industry-tried by slim Al-Si coated 22MnB5Nb PHS, under -20 °C dew points and without dew point control, and the U-shaped constant bending load test in 0.1 mol/L HCL solution of samples from components were performed based on automotive industry standard T/CSAE155-2020, to compare the hydrogen embrittlement resistance. The results were attained that, under same testing fracture stress, the fracture time is higher obviously for samples at -20 °C dew points comparing to the one without dew point control, and the atmosphere in austenitizing furnace affects prominently the diffusible hydrogen produced by reduction reaction in austenitizing process. A hydrogen embrittlement mechanism deduction is that the original diffusible hydrogen in steel and the diffusible hydrogen produced by reduction reaction in austenitizing process leads to initial micro cracking under higher bending stress according to HELP effect, after that microcrack passivates, and restart of microcrack by the effect of dislocation, grain boundary and applied stress, then hydrogen embrittlement fracture occurs by repeated microcrack passivation and restart.