Occurrence of rock mass in certain geological environments forms complex geologic body after a long geological tectonism. This geologic body is composed of rock material of continuous character and various geological structure planes of discontinuous character. Permeability is one of the important parameters affecting the permeability characteristics of complex rock mass. Permeability selected correctly or not is directly related to the reliability and engineering stability of the fractured rock mass seepage analysis results. Laboratory experiment methods are used to determine permeability of fractured rock mass combining with the principle of Darcy's law. Independent development of five pressure chambers of different sizes can measure the permeability of rock specimen in different sizes. Three types of experiment include stable seepage pressure experiment

variable seepage pressure experiment in one size and variable seepage pressure experiment in five different sizes. Experiment can get the permeability of rock specimen which is combined by different fractures and holes under steady flow and unsteady flow and also the permeability characteristics of multiscale rock. This method can determine the changing law of permeability along with the rock size increasing. Conclusions can be drawn from the multiple groups of experimental results. The rock seepage channel increases along with the rock size increasing

thus the permeability increases. But the permeability will be stable until it increases to a certain extent. And also this law can play a guiding significance to engineering.