Abstract: Based on a mercury injection test and fractal theory,a total of 32 coal samples from western Guizhou with different ranks were studied on their fractal characteristics in order to quantitatively describe the complexity of pore structure. The relationship between fractal geometry parameters,porosity and permeability of coal reservoir was also discussed. The result shows that the pore fractal dimension in this area could be divided into penetration fractal dimen- sion and proliferation fractal dimension. In addition,by using the pore volume ration as weights and the fractal dimen- sion of each diameter section weighted sum,the integrated fractal dimension could be calculated. At the same time,the penetration fractal dimension decreased with the increase of coal seam metamorphism,while the proliferation fractal di- mension and integrated fractal dimension increased with the increase of coal seam metamorphism. The fractal bounda- ry,proliferation pore volume fraction and total pore volume had a good correlation with the integrated fractal dimension and proliferation fractal dimension. Moreover,the correlation coefficient between integrated fractal dimension and anterior three parameters was higher than that proliferation fractal dimension and three parameters. The integrated fractal dimension,fractal boundary and proliferation pore volume fraction had a negative power exponent relationship with po- rosity,while a clear linear positive relationship was shown between total pore volume and porosity. Compared with pen- etration fractal dimension and proliferation fractal dimension,the integrated fractal dimension is more effective to ex- plain coal reservoir permeability.