A high precision analog quantity input and output module for train control on-board equipment was elaborated, which was mainly composed of analog quantity input circuit, analog quantity output circuit, fault free output circuit, processing system and communication sub-module. The design principle and implementation of the analog quantity input and output module were expounded. The test results showed that the module has good performance and high sampling accuracy, which could well meet the design requirements of analog signal acquisition and output for train control on-board equipment.