Abstract: Aiming at the problem of poor imaging quality due to focusing height error in three-dimensional imaging of multi-baseline circular synthetic aperture sonar, a three-dimensional imaging method for multi-baseline circular synthetic aperture sonar based on particle swarm optimization is proposed. The algorithm uses particle swarm optimization to estimate the focusing height error and compensate for the phase error caused by it, uses the hyper-beamforming method to improve the imaging resolution in the height direction, and combines the fast factorized back-projection method to accelerate the three-dimensional imaging speed. The effectiveness of the algorithm is illustrated by simulation analysis and lake trial data processing. The experimental results show that the method can achieve high-resolution three-dimensional imaging for the echo signals of multi-baseline circular synthetic aperture sonar.