Abstract: Hazard and operability (HAZOP) analysis is widely used and recognized as the preferred safety analysis approach in the chemical process systems. Compare with the manual HAZOP analysis，the computer aided HAZOP analysis has many advantages，such as good maturity，time saving，effort saving，and so on．However，the report of the computer aided HAZOP analysis has a huge number of HAZOP results and the important issues can not be separated from the general ones. The computer aided HAZOP analysis based on AHP was studied. The formation mechanism of disaster in process systems，the general formation of disaster in complex process systems，and the principles of fault and accident diagnosis，forecast and disasters prevention in complex process systems were investigated. Dangerous paths were sequenced according to their objective evaluation weights. The system provides a scientific basis for suggestions about preventing important potential danger and adopting programmed control system，interlock mechanism，or linkage. The analysis of nitrobenzene prefractionator by the SDG-HAZOP program based on AHP was taken as an example to formulate the actual application of the computer aided HAZOP analysis technology based on AHP.