In recent years,target detection algorithm based on deep learning has attracted much attention.In order to deeply understand the typical anchor-free object detection algorithms,the principle mechanism,network structure,core characteristics,advantages and disadvantages of seven anchor-free object detection algorithms based on deep learning were compared and analyzed.The performance of the above algorithms was experimentally studied.On this basis,the main characteristics of the anchor-free object detection algorithm were summarized,and the research direction of the anchor-free object detection algorithm was pointed out.