The invention aims to provide a non-smooth surface fluid friction resistance testing device and a testing method. The testing device comprises a pool, a buoyancy material, a support, a fixed pulley, a weight and a pull rope. A flat plate to be tested and the buoyancy material are fixed together, the pool is filled with fluid, and the flat plate to be tested and the buoyancy material jointly float on the fluid. The support is fixed to the position beside the pool, the fixed pulley is installed on the support, the pull rope is wound around the fixed pulley, one end of the pull rope is connected with the buoyancy material, and the other end of the pull rope is connected with the weight. The pull rope keeps horizontal between the fixed pulley and the buoyancy material and is higher than the wall surfaces of the pool, namely the tension exerted on the buoyancy material is equal to the gravity of the weight, the gravity of the weight is larger than the friction resistance of the flat plate, and thus the flat plate can move forward under the effect of gravity of the weight. The testing principle is simple and visualized, the testing device is different from other devices used for estimating a resistance reduction effect of a non-smooth surface, the friction resistance of the non-smooth surface can be directly tested, and the testing result is reliable.