The effects of high temperature annealing on the stability of the intrinsic defects in unintentionally doped epitaxial 4H-SiC prepared by low pressure chemical vapor deposition (LPCVD) are studied by electron spin resonance (ESR) and low-temperature photoluminescence (PL). The results showed that the concentration of intrinsic defects increases with increasing annealing temperature and reaches its maximum at 1573 K, then decreases with the gradually increasing annealing temperature when annealing time is 10 min or 30 min. The annealing temperature has an important effect on the concentration of intrinsic defects in epitaxial semi-insulating 4H-SiC prepared by LPCVD, whics is attributed to the process of intrinsic defects being stabilized and the strong interaction between the intrinsic defects during annealing.