The present invention discloses a APNT service positioning and integrity monitoring method and system. The method includes the following steps: determining a positioning accuracy requirement in a target scene; when the positioning accuracy requirement is high-accuracy positioning, determining a position of an aircraft by adopting a combined positioning algorithm, and monitoring the integrity of a combined positioning by adopting a multi-solution separation mode; when the positioning accuracy requirement is low-accuracy positioning, judging whether the aircraft is a high-altitude user; if not, adopting an air-to-air positioning algorithm for a high-altitude user and a low-altitude user based on LDACS to determine the position of the aircraft, and adopting a least square residual method to monitor the integrity of the air-to-air positioning. According to different requirements of users on positioning accuracy and actual application conditions, the present invention can provide a variety of APNT alternative solutions for an aircraft.