The present invention provides a LDACS-based air-ground cooperative positioning method. According to the method, on the basis of LDACS, users are classified into super-high-altitude users, high-altitude users, and low-altitude users, and air-ground cooperative positioning is implemented through information exchange among the users at the three levels. Meanwhile, a new fault mode and an integrity hazard are introduced into the method. Therefore, the present invention further provides a method for monitoring the integrity of a LDACS-based air-ground cooperative positioning method, including a fault detection algorithm and a protection level solving method; and proposes a method for evaluating the complexity of integrity monitoring. The LDACS-based air-ground cooperative positioning method provided in the present invention well solves the problem of the shortage of APNT services in poor terrain conditions, making the positioning results more accurate.