Gas transmission station is essential for long-distance natural gas transportation and its stable and safe operation matters. Non-routine tasks in gas transmission station have a significant hazard due to its high dependency on coordination between workers and strict operation procedures. Job hazard assessment (JHA) has been an effective method to decompose a non-routine process into steps and predict hazards of each step. However, people tend to ignore cumulative characteristics of risks with conventional JHA. To address this problem, the concept of cumulative risk is introduced to improve conventional JHA method. For illustration, the gas transmission startup process is chosen to apply the proposed method. First, the process is broken down into six steps in sequence and hazard preliminary analysis is conducted. Then the numeric risk matrix is used to determine risk value of each step by considering severity and possibility. Both independent risk and cumulative risk are evaluated and then compared. The results show that cumulative risk is more reasonable and practical and improves reliability of job hazard analysis. (C) 2016 Elsevier Ltd. All rights reserved.