The present invention discloses a GDOP analysis-based GSM-R interference source fusion positioning method, relating to technologies of wireless communication. The method comprises the following steps of determining monitor stations monitoring the same interference signal at the same time and estimating signal receiving quality of each monitor station; determining a region at where an interference source is according to interference signal receive powers of N screened monitor stations and a position relationship of the monitor stations; performing positioning error analysis on a general area of the interference source in different conditions; according to a positioning error analysis result, determining an optimal monitor station combination and a corresponding positioning system; and completing high-accuracy fusion estimation of the interference source position. Through adoption of the method, the GSM-R interference signal can be found more accurately and timely, and the interference source can be positioned.