Abstract: China Spallation Neutron Source (CSNS), as a high power proton accelerator, is designed to control the beam loss strictly, and the beam loss measurement system is very important for accelerator equipment protection, residual activator control and accelerator machine debugging. This paper analyzes the selection of detectors, analyzes the functions of preamplifier, introduces the hardware configuration of data acquisition system, the interface of local station and central control room, and emphatically introduces the application of this system in the beam debugging of different energy segments of accelerators.