An effective safety management requires attention to human factors as well as system compo-nents which make risky or safe situations at technical components. This study evaluates and ana-lyze ergonomic behaviors in order to select the best work shift group in an Iranian process in-dustry, in 2010.The methodology was based on the Ergonomic Behavior Sampling (EBS), and TOPSIS method. After specifying the unergonomic behaviors and with reference to the results of a pilot study, a sample of 1755 was determined, with a sampling accuracy of 5% and confi-dence level of 95%. However, in order to gain more confidence, 2631 observations were collect-ed. The results indicate that 43.6% of workers’ behaviors were unergonomic. The most frequent unergonomic behavior was amusing of legs while load lifting with 83.01% of total unergonomic behaviors observations. Using TOPSIS method, the most effective shift group and the least at-tractive alternatives for intervention were selected in this company. Findings declare high number of unergonomic behaviors. Catastrophic consequences of accidents in petrochemical industry ne-cessitate attention to workers’ ergonomic behaviors in the workplace and promotion of them.