Abstract: On November 22, 2013, the oil leakage of SINOPEC's Dongying-Huangdao Pipeline to municipal drains led to an explosion which killed 62 people, recording as the most serious pipeline accident. Later, the State Council set up a work team to investigate the process and causes of the accident and thereby to identify the liabilities. Based on the investigation report, the causes of the accident are analyzed. It is pointed out that security is more important than efficiency and economy in pipeline operation; incompliance of integrity management is a critical trigger for the accident; in the five elements of safe production, safety culture is still the weakest one. In order to ensure pipeline safety, it is necessary to strengthen the safety culture and practically implement the integrity management.