The invention relates to improvement of aircraft assembly quality detection and a measurement method of a rudder deflection angle in an aircraft developing test. In a measurement method of an aircraft rudder deflection angle, after an aircraft is parked, three laser tracker goal target sphere brackets are adhered to and fixed on a tested rudder surface; a laser tracker bracket is arranged in front of a goal target sphere so that a laser beam can directly reach all goal targets under various postures of the rudder surface; a laser tracker measures a space coordinate position of each measurement point on the rudder surface under different states, and the rudder deflection angle is obtained by calculating a measurement result by utilizing a plane group equation to realize the measurement of the aircraft rudder deflection angle. The invention simplifies operation steps, lowers the labor intensity, greatly enhances the measurement efficiency as well as also reduces the influence of human factors on the measurement result and enhances the measurement accuracy because the laser tracker is adopted to measure the accurate position of a target point, thereby more truly and accurately measuring the rudder deflection angle.