Neutral beam injection(NBI) heating is one of the most important auxiliary heating means of Tokamak(EAST) experiment device, and the RF ion source is the crucial part of the research of NBI system in institute of plasma physics. In order to diagnose the plasma parameters accurately, a Langmuir probe signal acquisition system is designed by using PXI as the platform in this paper. In the hardware part, it is mainly aimed at the problem of the interference of the 1MHz RF source in the process of producing plasma, so a 4th-order Butterworth low-pass filter is designed. The software part, which is based on LabVIEW, is designed to acquire and process the probe signal real-timely. The processed data is displayed on the GUI interface and stored on the local hard disk. The implementation of the system can effectively solve the problem of interference in the RF ion source test, improve the accuracy of the data acquisition, and provide a more reliable basis for the RF plasma discharge debugging.