Restraining the distortion of inertial navigation system in complicated environment is crucial for aircraft to achieve the long-endurance and high-accuracy autonomous navigation. Geomagnetic navigation can work at all-time， in all-weather and a passive way. The geomagnetic matching algorithm is the critical technology for geomagnetic matching navigation system. An improved united matching algorithm for geomagnetic navigation is proposed to improve the shortcomings of the mean square difference （MSD） algorithm that cannot correct the heading error and the iterated closest contour point （ICCP） algorithm that has poor real-time performance and diverges when greatly initial errors exist. It combines the rough matching and precise matching methods to determine the search range of precise matching process and reduces the initial error. Furthermore， to improve the real-time performance and efficiency in precise matching， a strategy based on the dynamic window is presented. The experiment results show that the algorithm meets the demand for long-endurance aircraft， effectively improves the real-time performance， raises the accuracy of positioning and restrains the distortion of inertial navigation system.