PID control schemes have been widely used in petroleum refinery and chemical processes. However, suitable tuning of PLD parameters in order to maintain product quality and stability of reaction processes is required, especially, where in the polybutene reactor with exothermic reaction, the process dynamics change greatly due to the change of the catalyst activity, the product grade, and so on. Therefore, the operator has to determine the parameters as fairly conservative values taking the stability of the reactor into consideration through trial and error. In order to overcome these problems, the authors have proposed a self-tuning PID control scheme whose PID parameters were tuned automatically following the change of the dynamics. In this paper, the effectiveness and implementation are investigated by applying the above method to temperature control of a polybutene reactor. In particular, it is shown that deterioration of the control performance due to wrong initial setting of the PID parameters is proved suffcient.