Sideslip angle is one of the important flight status parameters.Considering the true aircraft flight status a method for estimating the civil aircraft sideslip angle based on quick access recorder (QAR) data was proposed by selecting magnetic heading drift angle wind direction wind speed ground speed pitch and some other parameters from the QAR.The aircraft under the influence of westerly was taken as an example and the sideslip angle estimation procedure was derived by analyzing wind triangles of four kinds of heading and using the transform relationship among the earth-surface inertial reference frame body reference frame and wind coordinate frame.Finally a piece of QAR data was selected to estimate the sideslip angle.The result shows the effectiveness of this method.