Abstract: Magnetic induction communication is an emerging underwater wireless communication technology, but the traditional magnetic induction communication system has high path loss and limited transmission distance. In this paper, the point-to-point and cooperative magnetic induction communication models of the coreless circular coil are analyzed theoretically, and the optimal design methods of the coil placement angle in the cooperative communication model is proposed, so as to maximize the communication distance. At the same time, a correction mechanism is proposed to dynamically eliminate the influence of water flow under the actual underwater application environment. The research results show that for the general cooperative mode, when the interval angle is greater than 38.53°, the increase of magnetic flux of transmitting coil T₂ to receiving coil R₁ is less than 20%; the relative growth rate of magnetic flux at the receiver can be increased by changing the placement angle of T₂ and R₁, and can be increased by 20.3% and 12.66% respectively compared with the general cooperative mode at most, and the method of changing the placement angle of T₂ is more effective to improve the whole communication ability; when the minimum sensitivity of the receiver is 0.1 nT, the transmission distance of the cooperative magnetic induction communication with changing the placement angle of T₂ (coil spacing is 100 m) can be increased by 9.96% compared with the point-to-point mode under the same transmitting power.