SG-365 steel is an important material End used for manufacturing a pressure vessel and gas piping. In this investigation, the elastic plastic fracture toughness of this material is evaluated by the unloading compliance method according to the ASTM E8l3-97 and E1152-97 method on the smooth and side groove In specimens. The effect of smooth and side groove is studied on the elastic plastic fracture toughness. The side grooved specimen is very useful in estimation of the $J_{IC}$. Because it is much easier than the smooth specimen to the onset of the ductile tearing by the R curve method. Besides. it improves the accuracy of toughness values, decreases the scattering of them and crack tunneling effect and shear lip by the side groove.