In the environment of marine exploitation,underwater object detection technology is widely used. With the development of underwater robotics and computer technology,this technology is receiving more and more attention from researchers. According to the current research progress of underwater image target detection,a brief introduction of the underwater image target detection process(i.e.,image acquisition,image pre-processing and image detection methods ) is important for summarizing the current development status , discovering the shortcomings of the technology and exploring future research directions. The main advances in image acquisition, image pre-processing and image detection are discussed for the problem of underwater target recognition based on optical images,and the current development state of underwater image target recognition technology based on deep learning is described. By discussing and analyzing the process of underwater target processing,we point out the problems that need to be solved in the field of underwater image target recognition and predict the technical development trend in this field.