Abstract: A most promising way being considered for the disposal of radioactive waste is deep geological burial in rocks, such as granite and limestone.Diffusion measurements have been made on granite and limestone sampled from the suburbs of Beijing. 75Se(SeO32-) is used as a tracer simulating the long-lived 79Se. The diffusion experiment is carried out in a diffusion cell which is designed and fabricated in this laboratory. Details of the experimental technique and method of analysis are described and the most important diffusion parameters, namely, intrinsic diffusion coefficient Diy rock capacity factor and sorption coefficient K are given. The implications of the results are discussed.