In this paper, we manufactured the regenerated FBG by the thermal annealing of seed FBG based on UV irradiation. The writing conditions of regenerated FBGs were investigated in four types of optical fiber. FBGs written in $H_2$-free fiber were erased and not regenerated during the thermal annealing. FBG written in $H_2$ loaded Boron co-doped fiber was erased at the temperature of about $580^{circ}C$ and regenerated about $590^{circ}C$. However, the extinction of regenerated FBG started at the temperature over $900^{circ}C$ and then FBG disappeared out. FBG written in $H_2$ loaded Ge high doped fiber was erased and regenerated around the temperature of $800^{circ}C$ and maintained until the end of the thermal annealing. The reflection of the regenerated FBG was decreased about 12 dB and the center wavelength of the regenerated FBG was shifted about 0.7 nm compared with that of the seed FBG. The thermal characteristics of the regenerated FBG were analyzed by reheating from room temperature to $980^{circ}C$. As results, the regenerated FBG had survived without a decrease of reflection and the thermal sensitivity was $15pm^{circ}C$.