At present, the object grasping system of robot based on vision is one of the research hotspots, and it has a broad application prospect in industry, especially in the part of sorting. The key technologies of this system include robot hand-eye calibration, grasping target detection, grasping path planning, etc. This paper provides an overview about the current status of these key technologies by collating relevant literature, including the four kinds of hand-eye calibration methods, deep learning based grasping target detection algorithms, and the advantages and disadvantages of three kinds of grasping path planning methods. In this paper, the key technologies of vision-based robot object grasping system are summarized and prospected, which can be helpful to researchers in related fields.