UAV geophysical surveys can adapt to complex ground exploration environments and greatly reduce the safety risk of operators, which may be applied in geophysical surveys, geological investigations, resource exploration and other fields. Rotary-wing UAV is characterized by its flexible start-stop mode, high safety profile and night navigation. In this paper, according to the DY-115 rotary-wing UAV, an aeromagnetic measuring system with 115KG large load capacity was designed and integrated, and a magnetic compensation flight and test flight were successively carried out. The data satisfied the requirements of the technical specifications. By comparing and analyzing the test aeromagnetic anomaly data with the field magnetic data, the overall trend of the contour was observed to be basically the same as the shape. Accordingly, the aeromagnetic anomaly was found to be smoother and more continuous, which aligned with the interpretation and inversion of the anomaly, further verifying the stability, reliability and practicability of the large load rotary-wing UAV aeromagnetic measurement system.