Abstract: Partial discharge is a crucial indicator for evaluating the insulation condition of generators. To address the issues of low sensitivity and poor reliability in existing online monitoring devices, this paper designs a broadband capacitive coupler sensor and develops a partial discharge online monitoring system based on the ARM+FPGA architecture. Experimental results show that the system possesses high sensitivity and good reliability, enabling data acquisition and analysis for different discharge models. The proposed system demonstrates favorable applicability and engineering value for online partial discharge monitoring in generators.