At elevated temperature, very complex precipitations occur in STS316. To investigate the effect of the precipitation on mechanical properties in SIS316, tensile tests and fatigue crack growth tests were carried out at $650^{circ}C$ using artificially degraded materials. The material degradation was simulated by aging for up to 20000 hrs. at $750^{circ}C$, which is equal to 179000hrs (about 20yrs) of service life at $650^{circ}C$, after conducting solution treatment for 20 min. at $11300^{circ}C$. The result of the hardness test and the tensile test showed that both properties are closely related to the mean free distance of carbides. Also, from the results of fracture tests at $650^{circ}C$, ${ riangle}K_{th}$, after values were found to decrease as aging time and microstructure, as the volume fraction of $sigma$ phase increased.