An underwater towing device, including an underwater towing assembly and a fixing mechanism of the underwater towing assembly. The underwater towing assembly includes a first floating body, a second floating body, and a third floating body. The fixing mechanism includes a fairlead carrier and two supports disposed on two sides of the fairlead carrier. The first floating body, the second floating body, and the third floating body are connected together via a fixing frame. The first floating body, the second floating body, and the third floating body have streamlined and bilaterally symmetrical shapes and all are hollow to accommodate experimental equipment. The first floating body is a cylinder having a drop-shaped horizontal cross-section. The upper part of the first floating body is provided with a buoyancy reserve tank having an elliptic horizontal cross-section.