Abstract: The arc spraying coating and its tribology property are investigated in this paper. The binding force of the coating grain of steel consists of the mechanical force and the molecular force etc. The structure of boundary of coating grain is the oxide of iron and the micro-cavity. The binding force between the coating grains of QAl9-2 consists of micro welding and so on. Owing to the existence of micro-hole in the coating of arc spraying, the excellent property of friction and wear can be obtained,especially under the condition of a rapider sliding speed.The wear mechanism of coating of steel is the stripping wear of coating grain.