In this study, a series of laboratory experiments were performed to firstly analyze the characteristics of the pore structure in low-rank coal (R-o1000 nm), with a poor development of mesopores (100-1000 nm). The fractal features of adsorbed pores and seepage pores were defined and calculated using fractal dimensions D-2 (2.563-2.926) and D-4 (2.683-3.263), respectively. D-2 has a positive correlation with moisture content, while D-4 has a positive correlation with Ro and fixed carbon and a negative correlation with the volatile content. Both D-2 and D-4 have a weaker association with the ash yield and no apparent relationship with coal macerals, indicating that coal-forming materials and environments have little influence on the pore structure fractal characteristics. D-2 has a strongly correlation with the BET surface area (R-2 = 0.9026) and the average pore diameter (R-2 = 0.9841), again proving that D-2 can be used to characterize the pore structure fractal dimension of adsorbed pores. D-2 shows a negative correlation with the Langmuir volume (VI), but no apparent relationship with the Langmuir pressure (P-L), indicating that the pore structure of absorbed pores has little effect on methane desorption during the process of CBM exploitation. D-4 has weak positive correlation with permeability. Overall, fractal analysis is beneficial for better understanding the pore structure, methane adsorbability and seepage ability of low-rank coal. (C) 2016 Elsevier Ltd. All rights reserved.