The invention relates to a method and a device for absolutely positioning a measurement target by multi-sensor fusion, belonging to the technical field of target accurate measurement and positioning. The method comprises the following steps of: converting WGS (Wide-Band Satellite)-84 geodetic coordinates of a GNS(Global Network Service) 8 measurement target into Beijing 54 rectangular coordinates through analyzing information measured by multiple sensors; carrying out target identification by utilizing image analysis; calculating a distance between a positioning device and the measured target; and calculating a coordinate offset between the positioning device and the measured target by utilizing the pitch angle and the direction angle of a camera during measuring and the distance between the position of the positioning device and the measured target so as to obtain the Beijing 54 rectangular coordinates of the measurement target. The Beijing 54 rectangular coordinates can be converted into the WGS-84 geodetic coordinates as required to realize the absolute positioning of the measurement target and obtain the absolute positioning information of the longitude, the latitude and the altitude of the measured target. The speed information of the measurement target can be obtained by calculating the distance between the positioning device and the measured target, and the displacement time of the measured target during GNSS (Global Navigation Satellite System) positioning is obtained by adopting a method of calculating for multiple times to solve for an average value.