In order to provide theoretical guidance and reference for service life extension, the wear mechanism of 38CrMoAl/QT600-3 friction pair which was prepared by nitriding treatment under actual working conditions was studied in this paper. The wear test was carried out by means of the recipsrocating frication tester under the simulated working conditions in which the temperature was 180 ℃, the load was 10 MPa and the sliding speed was 20 mm/s, and all the experiments were conducted under the dry friction condition. The wear loss was measured from the thickness change of the samples before and after friction experiment. The thickness, hardness, microstructure and phase transformation of the friction pair were analyzed by digital micrometer, micro Vickers hardness tester, optical microscope (OM) and X-ray diffractometer (XRD), respectively. The surface morphology and composition of counterfaces were investigated by laser scanning confocal microscope (LSCM), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The experimental results showed that, after nitriding, the thickness of 38CrMoAl white layer composed of ε phase and γ′ phase was about 26 μm, and its average surface hardness was 1 112.8HV0.3. The diffusion layer of 38CrMoAl was composed of α phase and its hardness decreased in gradient. Even though the 38CrMoAl white layer was worn away during friction, the diffusion layer can still retain the high hardness. The white layer of QT600-3 was composed of ε phase, γ′ phase and graphite phase. The thickness and average surface hardness of QT600-3 white layer were 16 μm, 960.4HV0.3 respectively. After QT600-3 white layer was worn away, the hardness of diffusion layer which was composed of α phase and graphite phase rapidly decreased to the level of matrix. The results of wear test showed that, under the current experimental conditions, the wear process of 38CrMoAl/QT600-3 friction pair could be divided into three stages, 38CrMoAl white layer grinding with QT600-3 white layer, 38CrMoAl white layer grinding with QT600-3 diffusion layer and 38CrMoAl diffusion layer grinding with QT600-3 diffusion layer. In the first two stages, the friction coefficient curve was stable, and the friction coefficient was between 0.5 and 0.6. The wear mechanism of the first two stages was mainly abrasive wear and fatigue wear, and oxidation wear was observed in the second stage. In the third stage, the main wear mechanism was proved as heavy adhesive wear and typical oxidation wear. Serious scratches and gluing occurred on the friction pair in this stage, resulting in large oscillation of the friction coefficient curve. Based on the experimental results, the postponement of the third stage was particularly crucial since the service life of 38CrMoAl/QT600-3 friction pair mainly depended on the number of friction in the first and second stages. It was demonstrated that the increase of the hardness and toughness of the white layer can effectively improve the wear resistance and friction reduction during abrasive wear and fatigue wear. Furthermore, the improvement in the thickness of the white layer can significantly increase the friction times. Therefore, the service life of 38CrMoAl/QT600-3 friction pair can be extended by the enhancement in the hardness, toughness and thickness of the white layer.