Agricultural robot is an important branch of robot family, and it reshapes the modern agriculture industry via replacing human with machines. The definition and classification of agricultural robots were presented, followed by the analysis of its current status, application requirements and technical challenges. Therefore, the phases of agricultural robots were divided into three stages. Through investigating a broad spectrum of agricultural robots with in diverse productional scenes, totally five aspects of the key technologies of agricultural robots, i.e., the biological and environment perception, smart decision-making and control, dexterous robotic arm and hand operation, autonomous navigation, and end-terminal-cloud coordinated robotic system integration, were highlighted to foresee its developing trends. Relevant standard architecture was proposed to forge the foundation of agricultural robotics. The agricultural robot common key technologies were beneficial to the intelligent agricultural machinery and smart agriculture industry development, indicating that the agricultural robots were in rapid progress which can be seized to catch up and overtake international counterparts. Finally, the developing direction suggestions and roadmaps were given for guiding the domestic agricultural robot industry in the future.