In the high-power, high-speed rotation of the aviation power system, the role of the spline coupling is of the utmost importance. The high speed and high load conditions experienced by aeronautical splines frequently result in increased wear, which in turn affects the reliability of the aerospace power system. In this paper, a reciprocating sliding fretting friction and wear tester is employed to conduct tests on cylindrical samples of spline material under different loads. The variation of the friction coefficient with load is recorded, and the wear volume is measured using a laser confocal microscope. The relationship between different positive pressure loads and wear coefficients was then obtained by combining with Archard’s wear equation. Finally, the contact stress-wear coefficient relationship was obtained using Hertz contact theory and Gauss-Amp fitting. The results indicate that the wear coefficient exhibits an initial increase followed by a subsequent decrease as the positive pressure load increases. The inflection point is located near 8.7N (1100 MPa). The accuracy of wear calculations can be enhanced by utilizing wear coefficients that vary in accordance with different contact stresses. This is of particular importance when undertaking spline wear prediction calculations, as it allows for the accurate prediction of spline life.