Abstract: The influence of silicon on the formation and variation of fibrous martensite of low carbon Si-Ma dual-phase steel was studied by quantitative metallography, SEM and TEM. The results show that when superheating degree is given, the thickening rate of the fibrous martensite slows down with the increase of silicon content. In the structure of intermediate quenching specimen, the starting disappearing temperature of the fibrous martensite increases with silicon content of steel.