Abstract: In order to fully improve accuracy and reliability of safety assessment for complex systems， a risk evaluation model for complicated process by combining risk evaluation with HAZOP， LOPA and Bow-Tie analysis. Firstly， higher risk units in system are chosen by risk evaluation method， and detailed HAZOP analysis is conducted for such higher risk node. Secondly， LOPA is applied for scenarios with higher risk， and the residual risk level of accident is evaluated based on the semi-quantitative risk matrix， and HAZOP case library was enriched by means of LOPA; Finally， key activities to prevent the failure of IPL (independent protection layer) are identified useless working through Bow-Tie analysis， then the safety accident with heavy casualties or property damage caused by system unsafe behavior is fundamentally prevent. Taking the RFCC (residue fluid catalytic cracking) equipment in Liaohe Petrochemical Industry Company as an example， the applicability and reliability of the model were verified through field application.

Key words: risk evaluation, HAZOP, LOPA, Bow-Tie analysis, safety evaluation