The use of bistatic radar consisting of Global Navigation Satellite System (GNSS) and ground-based receiver to detect water targets is an emerging method of monitoring waterborne traffic. This paper uses the Range-Doppler (RD) maps generated by the reflection signals of geosynchronous orbit (GEO) satellite to achieve target detection. In order to improve the signal-to-noise ratio (SNR) of moving target’s echo signals in the RD maps, an algorithm for enhancing the energy of the echo signals is proposed. The algorithm firstly moves the echo signals on the adjacent range unit and Doppler unit to the position of the weak echo signals by range and Doppler compensation, and then increases the energy of echo signals by signals accumulation, thereby achieving the purpose of enhancing the SNR. This paper describes the experiment of detecting freighters on the Yangtze River. The experimental results show that the SNR of the echo signals of the moving target is increased by about 4 dB on average after processing according to the algorithm，which verifies the feasibility of using the Beidou GEO satellite to detect the water targets.