A dynamic mathematical model is developed For the ethylene dimerization reactor to simulate the distribution of butene-1 and other oligomers in the products under different operating conditions. The bifurcation analysis of the model shows that the system can exhibit two types of static behaviour: unique and hysteresis. For both cases, the local optimum yields for butene-l correspond to unstable steady states. Studying the: effects of the recycle Row rate, the cooler heat transfer coefficient shows the importance of providing an efficient heat removal system for the reactor to operate around optimum conditions.