The invention relates to an unmanned aerial vehicle (UAV) for river water sample testing. The UAV comprises a main body, two support frames and four propellers and further comprises two floating mechanisms and two sampling mechanisms, wherein the sampling mechanisms comprise lifting and lowering assemblies and sampling assemblies; the lifting and lowering assemblies comprise driving units, telescopic frames, lifting and lowering plates, hinge blocks and moving blocks; the sampling assemblies comprise sampling boxes; sampling units, sample taking barrels, pistons and sample taking tubes are arranged in the sampling boxes; the floating mechanisms comprise rotating assemblies and floating assemblies; and the floating assemblies comprise floating air cushions and first air pumps. The UAV for river water sample testing is capable of realizing the function of multiple-site sampling through the sampling mechanisms, improving the work efficiency of the UAV, enabling the UAV to float on the water through the floating mechanisms, improving the floating effect, and improving the safety of the UAV.