Balanced homodyne detection technology is one of the best methods for detecting the quantum noise of a quantum state in continuous variable quantum information. In the balanced homodyne detection system, a pair of detectors with the same performance are needed to effectively detect the noise limit and the quantum fluctuations of quantum states for totally eliminating classical noises. Based on the Kirchhoff current law and the scheme of photodiodes in series, a type of balanced homodyne detector with excellent capability is designed and set up. The photo-current signal is obtained from the series connection nodes of photodiodes and then amplified, thus the requirement of identity for the two detectors is degraded and the quality of the balanced homodyne detection system is improved at the same time. The experimentally measured common-mode rejection ratio (CMRR) of the detector is 39 dB at 2 MHz. The improved detector with low noise, good linear gain and high CMRR can satisfy the requirements of quantum information experiments.