The effect of hydrogen on crack propagation of dual phase steel has been studied by hydrogen charging. The results were summerized as follows 1) The stress intensity value of dual phase steels in stage 1 increased with increasing martensite volume fraction. 2) The crack growth rate of dual phase steels in stage 1 was decreased with increasing martensite volume fraction. 3) The stress intensity value and crack growth rate were reduced by the hydrogen charging. 4) The fracture appearance of the hydrogen charged materials was predominantly intergranular fracture.