The effect of pressure on the phase transformation in Fe-30Ni-0.35C Alloy and pure metals was investigated by using PDSC(pressure differential scanning calorimeter). As the pressure increased from 1 atm to 60 atm, the $A_s$points of the ausformed martensite and the marformed martensite in Fe-30Ni-0.35C Alloy were lowered about $2~4^{circ}C$ at reverse transformation. This is why the volume change came down at phase transition(from martensite to autenite). As the pressure increased from 1 atm to 60 atm, $A_f$ points were constant or slightly increased. This is due to the promotion of carbide precipitation with increasing pressure. The enthalpy change of the ausformed martensite in Fe-30Ni-0.35C Alloy was increased by 10~14J/g. The melting points of the pure metals, Se, Sn, Pb, Zn and Te were slightly increased with increasing pressure. The enthalpy changes of the pure metals at melting were little changed or slightly increased with increasing pressure.