Through the application of the principles and methods of fractal geometry to the study of fractal characteristics of the two-dimensional distribution of three different fracture systems in the Dexing porphyry Cu orefield, the authors found that these fracture systems not only possess the statistical self-similar character in the scale extent studied, but also h,v/e different D values of fractal dimension in different ore districts and fracture systems. As a result of this study, the D values of fractal dimension in the sub-range of mineralized porphyries are higher than that of the whole orefield, and that of the NE fracture system is slightly higher than the WNW fracture system. The characteristic distribution of D values coupled with comparison of the attitudes, penetration relationships and ages of different fracture systems with the location of porphyry Cu ore bodies indicates that the higher the D value, the more favorable the conditions of Cu ore formation and larger the deposit size and that the NE- and WNW-trending fracture systems play an important controlling role in ore-forming processes.