Nowadays, with the popularization of low current device in railway communications, sensors and other aspects, electromagnetic interference has attracted more and more attention, however, the work about the coupling analysis of electromagnetic interference mechanism is rare. This study focuses on a typical electromagnetic interference problem of rail pressure sensors. First a physical model of capacitive coupling between power and signal lines is established based on the investigation of interference sources. Then the distributed capacitance parameters between cables are extracted, and the value of coupling electric field is quantitatively analyzed. At the same time, the interference source is identified and the capacitive coupling voltage interference caused by power line crosstalk is determined. Corresponding measurements of suppressing interference are provided, which verifies the analysis. The results show that the grounding device has a great influence on the electromagnetic interference of signal voltage. When the buried depth of the grounding resistance increases from 0. 1 m to 0. 6 m, the electromagnetic interference voltage of the power line is suppressed. Furthermore it′s found that the connecting end of signal line is a weak link valuable to the electromagnetic interference, which is the key to improve the shielding efficiency. The mechanism analysis and calculation method of capacitive coupling proposed in this paper and the suppression measures of electromagnetic interference of sensors can provide a general reference for suppressing the electromagnetic interference of electrical equipment in engineering K .