Beamforming is an important part of sonar signal processing and a prerequisite for sonar to detect and recognize underwater targets effectively. According to the different sonar forms

it can be divided into linear beamforming

planar beamforming and circular beamforming. The circular array is simple in structure

usually fixed on the platform installation

and compared with the tow line array

it avoids the problem of formation correction

and the circular array has the ability to distinguish the left and right sides of the underwater target

and has the ability to detect the pitch direction

so it has been widely concerned. The robustness and high azimuth resolution of common circular array beamforming methods are contradictory

and the performance is poor at low signal-to-noise ratio. In order to improve the detection ability of circular array on underwater targets

a new circular array beamforming method is proposed in this paper. Firstly

diagonal load reduction technology is used to suppress background noise

and then semi-definite programming technology is used to achieve high resolution azimuth estimation of targets. Thus

it still has good ablility of detection under the condition of low signal-to-noise ratio.