The invention belongs to the power transformer equipment partial discharge on-line monitoring technical field and relates to an optical fiber external cavity type Fabry-Perot sensor array-based transformer partial discharge detection system. The partial discharge detection system is composed of a narrow-band light source, an optical filter, an optical splitter, four optical circulators, four single-mode optical fibers, four optical fiber external cavity type Fabry-Perot sensors, four photoelectric detectors, four amplifiers and an oscilloscope, wherein two optical fiber external cavity type Fabry-Perot sensors are arranged in oil in temperature measuring grooves at the top of a transformer, and the other two optical fiber external cavity type Fabry-Perot sensors are arranged in flange grooves at two sides of the top of the transformer; and the groove structures can be equally adopted as ultrasonic signal collectors and can be used for removing angle response, enhancing signals and avoiding the influences of internal oil pressure of the transformer. The optical fiber external cavity type Fabry-Perot sensor array-based transformer partial discharge detection system of the invention has the advantages of high sensitivity, strong signal collection ability, convenient operation and strong anti-interference ability, and can greatly detect the partial discharge situation of the transformer with no additional auxiliary structure required. The optical fiber external cavity type Fabry-Perot sensors have high sensitivity and can detect weak partial discharge signals.