Designed is an onboard balanced photoelectric detector with high sensitivity, which is composed of a balanced photodiode chip and a transimpedance amplifier. The balanced photodiode chip adopts the internal balance structure of dual InPInGaAs photodiode unit to reduce the noise of the chip itself and improve the detection sensitivity. The closedloop amplifier integrated with positive and negative bidirectional current input circuit, automatic gain control circuit and inverter input circuit was simulated by Cadence software, and the relationship of the equivalent noise power, bandwidth and gain was obtained. Then a tranresistance amplifier being adaptive to balanced photodiode chip was produced. A 1.55μm laser test system was set up to test the performance of the developed detector, and the results show that its 3dB bandwidth of 1.58GHz, equivalent noise power density of 5.96pW/Hz1/2, and the commonmode rejection ratio of 42.04dB (@DC~1.58GHz) are realized, and the receiving sensitivity in the coherent laser communication system reaches -61dBm.