With the popularization of multiprocessor systems and network applications,the study of dependability of systems has become an unportant research area of computer science. A 'Boolean equation diagnosis' method is firstly presented for test model of system-level fault diagnosis, and the correctness of the equations has been proven. The Boolean equation is more concise than the graph method in test model representation. Based on the equations,the methods to compute optimal diagnosis, the set of consistent fault pattern,absolute good processors and bad processors are presented. And some theorems about the relationship among different test models on the set of consistent fault pattern and diagnosibility are proved. It is a useful attempt in theory and practice of system-level fault diagnosis.
