By X - ray analysis and metallographic analysis,it was found that after the QPQ complex salt bath heat - treatment there are Fe3O4 and Fe2N in the nitrided layer of alloyed grey cast iron with different microstructures which was heat treated under different conditions of heating,heat preservation and cooling,higher the content of ferrite in composites was,larger the thickness of nitrided layer is,The wearing rate of alloyed grey cast iron with different microstructures before and after QPQ complex salt bath heat - treatment was compared,and it was found that after the QPQ complex salt bath heat - treatment the wearing rate was 1. 6% ～ 5. 7% of that before QPQ complex salt bath heat - treatment.