Abstract: Dark currents within an accelerator system may lead to superconducting cavity energy loss, and also have the potential to destabilize the superconducting accelerator. In response to this challenge, a high-precision dark current monitoring system has been developed to protect the accelerator. This article offers a comprehensive description of the Faraday cup probe and high-precision data acquisition system, encompassing the hardware parameters and software architecture. A detailed test of performance was also done, the multi-step I/V converter at the most sensitive state is a 23 Hz bandwidth, a signal-to-noise ratio of 61.49 dB and a resolution of 7.47 mV for the data collector. System test results show that it exhibits good linearity in DC or AC condition. Furthermore, the article presents measurements of the system's resolution and signal-to-noise ratio across various ranges, demonstrating that the resolution can reach 37.7 pA and the signal-to-noise ratio can reach 32 dB in the most sensitive range.