Agricultural internet of things (Ag-IoT) is the highly integrated and comprehensive application of the new generation of information technology in agricultural field. Ag-IoT is playing an important leading role in the agricultural informationization of China. It has changed the traditional agricultural production mode, and it is also promoting the transformation from the traditional agriculture to intelligent and precision agriculture. The concept of Ag-IoT and its technical system framework were firstly introduced. Then the research status and advances of sensing technologies, communicating technologies and key application technologies used in Ag-IoT were reviewed in detail. The challenges and problems existing in the development of Ag-IoT in China were further analyzed. Based on the analysis, countermeasures for the applications and development of Ag-IoT of China in many aspects were proposed, such as research priorities, development layout, advancing directions, application models and mechanisms for sustainable development.