The invention relates to an intelligent monitoring system for a beam end expansion device of a long-span railway steel bridge. The intelligent monitoring system comprises an environmental impact variable monitoring sub-module, a main guide bridge beam end displacement monitoring sub-module, an expansion device main body monitoring sub-module, a beam end running condition monitoring sub-module anda rail inspection vehicle beam end detection sub-module. Through adoption of the intelligent monitoring system, intelligent monitoring of the beam end expansion device is realized, and monitoring content covers environmental impact variables; main lead bridge end displacement monitoring is realized; longitudinal and lateral displacement monitoring of the expansion device, vertical deflection and strain monitoring, and video monitoring are realized; beam end driving state monitoring is realized; and access to rail inspection vehicle detection data is realized. The intelligent monitoring systemrealizes automatic real-time monitoring and evaluation of the working state of the beam end expansion device, has the functions of intelligent monitoring, data analysis and evaluation, and state prediction and diagnosis, covers the monitoring of various static and dynamic parameters of environments and structures as well as driving state, and provides technical reference for the engineering department.