Flight plan route segment automatic activation method

In order to solve the technical problem that an existing route segment automatic activation method is tedious and redundant in calculation, the invention provides a flight plan route segment automaticactivation method. The flight plan route segment automatic activation method comprises the following steps of: 1) acquiring a current position of an airplane and a magnetic difference thereof, and acquiring longitude and latitude of waypoints P1, P2 and P3 and magnetic difference thereof; 2) calculating magnetic course angles from the waypoint P2 to the waypoint P1 and from the waypoint P2 to thewaypoint P3; 3) calculating a magnetic course angle from the waypoint P2 to the current position point A of the airplane; 4) and subtracting a magnetic heading angle (from the waypoint P2 to the current position point A of the airplane) from a magnetic heading angle (from the waypoint P2 to the waypoint P3), marking an absolute value of an obtained difference value as K1, subtracting a magnetic course angle (from the wayp