In order to study the seepage characteristics of rock mass containing periodic fractures with partial filling, an analysis model for the seepage of rock mass was built. Two boundary conditions were given for the interfaces between different medium in the model: 1) equal velocity; and 2) continuous shear stress. According to the given conditions, the velocity distribution in the fractures was deduced by using the Navier-Stokes equation and that in porous medium was deduced by using the Brinkman-extended Darcy equation. The equivalent permeability of rock mass containing periodic fractures without partial filling was also derived. A test equipment was made to carry out the equivalent permeability tests. In the tests, concrete and sandstone were used to simulate rock and filling fractures between two pieces of concrete. The difference of the results measured by tests and the equivalent permeability calculated from the theoretical expression was very small. The test result validates well the derived expression.