The Wudalianchi volcanic group is one of the youngest volcanic groups among the Cenozoic ones. As a typical example of intracontinental monogenetic volcano, it is characterized by clusters of small volcanic cones. A 1:5000 high-precision gravity survey is carried out in the western part of Wudalianchi to obtain the fine distribution features of regional magma chambers. This paper introduces the gravity density inversion method constrained by spectrum characteristics to obtain a three-dimensional underground density model of the region, and provides the spatial distribution of magma chambers based on their low-density features. There are three magma structures extending along northeast faults 5~10 km west of the Wudalianchi volcano, which appear as medium-high mountain landforms. There are two large magma chambers below the crater, and a large magma chamber at the depth of 30 km, which effectively supplies the formation of Wudalianchi volcano. Based on the density inversion results of this high-density gravity survey, it is revealed that magma structures exist at different depths in the Wudalianchi volcanic area, and it is proved that there are different stages of magma activities in this area, and that the formation of volcano is closely related to its faults. Such discoveries will provide important basic data for the further studies of the volcano.