To enhance the high-temperature performance of the fiber Bragg grating array (FBGA), an on-line writing high-temperature resistant FBGA is proposed. FBGA is coated with polyimide and is written on the drawing tower by single laser pulse with phase mask technology. After continuous processes of repeated coating, drying and final imidization, the final coating diameter, central wavelength, and reflectivity are 145-150 μm, (1551.35±0.1) nm, and 0.06%, respectively. The transmission loss of polyimide-coated FBGA (PI-FBGA) is 1.601 dB/km at 1550 nm. Additionally, the thermal stability and reliability of polyimide-coated FBG were studied. The findings reveal that the on-line writing high-temperature resistant PI-FBGA has excellent thermal stability and reliability and can be used for a long term below 300 ℃ and for a short time between 300 ℃ and 400 ℃. The high-temperature resistant PI-FBGA has vast application potential in petrochemical, environmental monitoring, aerospace, and other fields.