Abstract: The concepts of system place-state （PS） and anticipative PS were firstly proposed based on the application of the black box technology to the system testing of distributed software．As the test case controls the system PS and a fuzzy occurs between the system PS and the anticipative PS‚the fuzzy implication logic was next used to study the sys-tem testing．It was then concluded that the action relation of the test case to the anticipative PS was a fuzzy control re-lation and that the degree of control depended on the quality of software．The standard value of the tested software to pass the test was then obtained from the fuzzy control relation and fuzzy inference rules‚thus quantifying the judgment for software to pass the test．Quantified pass-rules in the system testing were finally put forward and applied to improve the automatic testing tool‚by which the efficiency of the test improved and the test cost was reduced．

Key words:  software system testing, fuzzy control relation, pass-rule