With the development of science and technology, simulation technology has been widely applied in the aerospace, power grid, medical and health care, financial, social and other fields. Under the traditional simulation environment, usually the operation of the simulation model in the ideal state, running status of model in the real environment is unable to predict in advance. Fault injection is artificially produced and introduced to the target system, thus accelerate the system errors and fault assessment technology. In system modeling and simulation phase, using fault injection could find the system error and improve system reliability. Through the analysis of the system fault, this paper puts forward the abstract definition of fault, uses variation patterns to describe the fault behavior, and gives ST_Net Petri net system and meta model definition of fault, discuss the injection mechanism and influence of the properties of variation pattern.