An expert system for neutron activation analysis has been designed on personal computer. It is mainly structured by means of the MDBS GURU, and composed of three subsystems: spectrum analysis, experiment design and data management. The gamma spectra from multiple channel analyzer can be treated conveniently with conventional methods and/or intellectualized isotope identification based on expert experiences. Fuzzy variable and its algebra are employed for inferring and expression of some conclusions. A procedure for quality control has been created to check the analytical quality. Suggestion of planning an experiment for a certain material can be obtained, and a gamma spectrum can be predicted or simulated. There is a data bank for saving the element concentrations.