Abstract: Geometric characteristics of the fault system as indicated by the three seismic reflection layers T₁,T₁,T₁ are studied by using fractal theory in Kerkang oil filed of Zhangqiang depression.As a result,the authors find that these fault systems are statistically self-similar within the scale range studied (r=0.5cm to 8cm).But different fault systems have different fractal dimension values D that reflect the complexity of their geometry.The size,number and spacing of faults within the same scale range may affect the magnitude of D obtained by box-counting method.There is a good correlation between D and the percentage of the individual fault system in different subregions divided.A comparision of the results of different subregions of different reservoir types shows that D value in the east subregion is higher than that in the west subregion for T₁,and that the D value in west subregion is slightly higher than that in the east subregion for T₁.It is shown that the higher the D value,the larger the oil-gas abundance (oil-bearing area or output of oil,gas and water) in the subregions.Such a relation between D values of fault systems and oil-gas distribution will provide a clue for researching the accumulation of oil and gas and their prediction in petroliferous basins.