Background and aims: Control room is a palpitating Heart of a system, and any error in operator’s duties has irreparable consequences. Nowadays, in many work places such as nuclear industry, military and chemical parts human error can cause catastrophic event that led many events around the world, so the purpose of this study is analyzing human error in a utility unit control room of a Petrochemical Company using Heart method. Methods: Data collection was done by direct observation methods, interview with "Bordman", senior shift, boss of Fuel vapor, related experts and analysis of previous incidents that occur. Then job analysis and human error identified respectively by HTA and TRACEr technique. Additionally, the error probability determined with Heart techniques which is a one of the tools of human reliability assessment. Results: The most important factors in incidence of human error at the control room operators were: fatigue, experience, consciousness, complexity of information, focus error and Error producing conditions were diagnosed: mental stress, High workload, focus, clear guidelines, lack of training and the task adaptation,. The most calculated likely error in the duties: reload bugs, boiler commissioning, control of production, maintenance, warning signs control.Conclusion: the results can be acknowledged that supervisor duties "Nobatkar" control room because of a high sensitivity range of error likely to have occurred and solutions must be proposed.This technique for this group should be priorited.