Abstract: The IGSQN (interactive graphic simulation of queueing retwork) facilitates performance evaluation and behavior study of queueing network system It provides an interactive graphic environment for entire simulation process (modeling/experiment planning/running/result analysis), and is designed to be independent of specific simulation languages. It's a useful tool for the user without any simulation programming experience. The program, written in FORTRAN 77 and PLOT 10, has run on Honeywell DPS8/49 with TEK. 4109 graphic terminal. In this paper, the features, structure and implementation of IGSQN are presented.Also an example is given.