The invention belongs to the technical field of mechanical test equipment and provides a flange tensile-bending composite loading multi-bolt loosening testing machine, which can simultaneously apply tensile-bending-torsional composite load to a multi-bolt connected flange to study the bolt loosening characteristics. Transverse load generated by a three-phase asynchronous motor is taken as bendingload applied to the flange, and tensile force generated by a hydraulic puller is taken as axial tensile load. The testing machine, different from a conventional apparatus that applies two types of composite load to a single bolt, can apply two types of composite load to the multi-bolt connected flange. The two types of composite load can be isolated from each other and do not interfere with each other, and load applied can be displayed in real time.