The invention provides a light power testing system which is connected with optical fiber communication equipment through an optical cable line. The light power testing system comprises an optical splitter and a light power meter, wherein the optical splitter is used for receiving optical signals of the optical fiber communication equipment, and the light power meter is connected with the optical splitter. The light power meter comprises a photoelectric detector, an I/V converting circuit, a program-control amplifying circuit, a lowpass filtering circuit, a negative feedback correction circuit, an A/D converting circuit, an FPGA data processing module and a power source module which are sequentially connected, the negative feedback correction circuit is composed of a differential input device and a voltage follower, and the power source module supplies power to the FPGA data processing module. The collected optical signals are transmitted to the lowpass filtering circuit after being processed, output voltage signals pass through the negative feedback correction circuit composed of the differential input device and the voltage follower, accurate input can be carried out on the collected and amplified signals in real time, input errors can be greatly reduced, and the measurement accuracy of the optical signals is improved.