Aiming at the difficult technical problem that the current domestic photoionization detectors are not able to be widely used due to its low accuracy and high cost, a method to separate the radio frequency UV lamp driver module and the weak current detection module was proposed by the improved structure. Based on the principle of photoionization and anti-electromagnetic interference, the detector mechanism and the method of reducing noise were discussed in depth, and the demodulation circuit modules such as power module, UV lamp driving module and weak current detection module were designed and developed. Special shell structure was designed to reduce noise interference caused by high voltage alternating current to weak current detection module while shielding external interference, so as to improve the measurement accuracy of the detector. A test and calibration system for the overall detector was constructed. The theoretical and experimental results show that the detector has good linearity, good repeatability (1.8%), stable operation at room temperature, and can be applied to the real environment. Meanwhile, the detector of this design has the advantages of small size, high sensitivity and fast response. It provides a reliable solution for the ease of use and real-time measurement.