The invention discloses a quad-rotor mini-type underwater vehicle. The quad-rotor mini-type underwater vehicle comprises a vehicle body, four both-way propellers and connecting pieces used for installing the both-way propellers. The quad-rotor mini-type underwater vehicle is characterized in that every two of the four both-way propellers are in one group, the two groups of the both-way propellers are symmetrically arranged on the two sides of the vehicle body respectively, propeller rotating shafts of the both-way propellers are obliquely arranged relative to the horizontal plane, and generated propelling force has the component in the heading direction; and the inclination angles of the propeller rotating shafts of the both-way propellers relative to the horizontal plane are equal, the two both-way propellers in each group are distributed in front of and behind the vehicle body, and the propeller rotating shafts of the both-way propellers are opposite in inclination direction. The quad-rotor mini-type underwater vehicle is reasonable in arrangement, the structure is more stable, movement is more flexible, and the vehicle can directly move in the vertical direction, namely, floating or descending. The overall structure is simple, and miniaturization and microminiaturization are facilitated. Conventional products can be adopted in all modules, special requirements are avoided, the independence of the underwater vehicle is guaranteed, and the beneficial effects of low cost, high stability and the like are achieved.