The hydrogen trapping phenomena in two bainite/martensite dual-phase high strength steels(U20Si and U20DSi)were investigated by electrochemical permeation technique.The hydrogen diffusivity was calculated from data of permeation delay time,and the diffusion coefficient in U20 Si is far less than that in U20 DSi.Moreover,the hydrogen diffusivity decreases as the volume percent of retained austenite increases.The experiment results show that there are different hydrogen trappings and different volume percents of retained austenite in U20 Si and U20 DSi.The retained austenite is precipitated as films.The trap binding energy for the retained austenite and hydrogen is calculated to be 40.4kJ·mol-1. The hydrogen trapping phenomena in two bainite / martensite dual-phase high strength steels (U20Si and U20DSi) were investigated by electrochemical permeation technique. Hydrogen diffusivity was calculated from data of permeation delay time, and the diffusion coefficient in U20 Si is far less than that in U20 DSi. Moreover, the hydrogen diffusivity decreases as the volume percent of retained austenite increases. the experiment results show that there are different hydrogen trappings and different volume percents of retained austenite in U20 Si and U20 DSi. The published austenite is precipitated as Films. The trap binding energy for the retained austenite and hydrogen is calculated to be 40.4 kJ · mol -1.