In this paper,radar graph fractal method is introduced to describe wear debris boundaries. Research results show that it is a nice way to describe wear debris boundaries. Since the longest axis is selected as the first coordinate axis,its center point selected as the center point of the radar graph,and the co-ordinate value of wear debris boundary selected as the measure parameter,the limitations existing in Yard fractal measure method can be avoided. For any wear debris,its radar graph fractal dimension value is one and only,and as the wear debris shape changes from round to strip,the radar graph fractal dimension value also changes from low to high,showing strong uniqueness and independence. Due to the fact that the researched wear debris is gotten in different wear states,the results also prove that radar graph fractal dimension value is correlated with frictional pairs work condition and wear state. Radar graph fractal method is compared with Yard fractal measure methods,and results show that ra-dar graph fractal dimension values gotten from different wear debris have enough value grads to avoid effect of errors,and provide higher sensitivity for wear debris shape. This paper also discusses the influencing factors for radar graph fractal method. With the increase of the decomposing degree value,the radar graph fractal dimension tends to keep stable at one certain value,showing the typical characteristic of the fractal theory. All this proves that radar graph fractal method is an effective description method for wear debris boundaries. Research results show that it is a nice way to describe worn wear debris boundaries. Since the longest axis is selected as the first coordinate axis, its center point is selected as the center point of the radar graph, and the co-ordinate value of wear debris boundary selected as the measure parameter, the limitations existing in Yard fractal measure method can be avoided. For any wear debris, its radar graph fractal dimension value is one and only, and as the the wear debris shape changes from round to strip, the radar graph fractal dimension value also changes from low to high, showing strong uniqueness and independence. Due to the fact that the researched wear debris is gotten in different wear states, the results also prove that radar graph fractal dimension value is correlated with frictional pairs work condition and wear state. Radar graph fractal method is compared with Yard fractal measure methods, and result s show that ra-dar graph fractal dimension values ​​gotten from different wear debris have enough value grads to avoid effect of errors, and provide higher sensitivity for wear debris shape. This paper also discusses the influencing factors for radar graph fractal method. With the increase of the decomposing degree value, the radar graph fractal dimension tends to keep stable at one certain value, showing the typical characteristic of the fractal theory. All this proves that radar graph fractal method is an effective description method for wear debris boundaries.