Abstract: Industrial high-carbon steel of 60Si2CrV, CrWMn, Mn13 and GCr15 were heated and quenched in order to obtain martensite. The morphology and substructure of martensite were observed by optical microscopy, scanning electron microscopy and transmission electron microscopy, and the formation mechanism of martensite also was studied. The results show that the martensite in high-carbon steel was plate martensite and the cryptocrystalline martensite also was plate martensite in fact. The substructure of the martensite in high-carbon steel mainly included twin crystal, and also included high-density dislocations. Martensite could nucleate not only in austenite crystal grain interior, but also at austenite crystal grain boundaries, twin crystal boundaries and the phase interfaces. It was considered that martensite morphology was essentially affected by volume strain energy during martensite phase transformation and the formation of substructure was closely related to the volume strain energy.