Abstract: In the helium purification system of 10 MW high temperature gas-cooled reactor (HTR-10), an experimental system which could be used to sample the radioactive graphite dust in the primary loop was designed and built. Combined with international research results, a simulation was done according to parameters of the helium purification system of HTR-10. The results indicate that the experimental system can sample the radioactive graphite dust effectively. The sampling filter can be disassembled easily for further measurement, and used to do a long term systematical study on the radioactive graphite dust. It can provide the informations of the graphite dust and the activity of solid fission nuclides in the primary loop in different operation situations, and supply large amount of important experimental data to study the behavior of fission products in HTR-10.