Abstract: Introduction The site laboratory in nuclear power plant is the important technology building,and the auxiliary process system served is also important to provide the better process system design. Method This article took the site laboratory in Hongyanhe nuclear power plant as an example,and discussed the auxiliary process system. Result The results summarize the layout principles of radiation zoning according to the characters and source of the sample, and the system which for being slightly radioactive-sewage recovery and the design principles of piping layout and so on. Conclusion This article provides the useful experience for the process system design of site laboratory in nuclear power plant in the future.