Abstract: Using methods such as magnetic Barkhausen noise （MBN） analysis, scanning electron microscopy analysis and mechanical property testing, the magnetic properties, microstructure and mechanical properties of P92 steel with different service durations were analyzed, and the effects of service time and microstructure changes on MBN signals were studied. The results show that during the service process of P92 steel, the MBN signal changes significantly. As the service time increased, the MBN signal first remained stable, and after serving for 30 000 hours, the MBN signal rapidly increased. The precipitation and coarsening of precipitated phases during service were the main reasons for changes in MBN signals, especially the size of Laves phase, which had a significant correlation with MBN signals. When P92 heat-resistant steel was in service for 30 000 hours, its high-temperature mechanical properties significantly decreased, followed by a slow decline thereafter. The MBN signal increased with the decrease of tensile strength, and the sensitivity of MBN signal changes was higher than that of mechanical property changes.