The invention discloses a power transformer partial discharge detection system based on a fiber bragg grating, which comprises an LD (Lead Detector) pumping source, a wavelength multiplexer, an erbium doped fiber, an isolator, a first fiber coupler, a second fiber coupler, a first fiber bragg grating, a second fiber bragg grating, a photoelectric detector, an acoustic emission collection card anda computer, wherein two input ends of the LD pumping source, the wavelength multiplexer, the erbium doped fiber and the first fiber coupler are in the same loop to form an annular cavity erbium dopedfiber laser; one output end of the first fiber coupler is connected with the first fiber bragg grating, the other output end of the first fiber bragg grating is connected with one input end of the second fiber coupler; one output end of the second fiber coupler is connected with the second fiber bragg grating, the other input end of the second fiber coupler is connected with the photoelectric detector; and the photoelectric detector is connected with the computer through the acoustic emission collection card. The power transformer partial discharge detection system is used for carrying out inservice real time and continuous monitoring on a transformer, and has the advantages of strong anti-electromagnetic interference capacity, small temperature influence, high detection precision and good flexibility.