A study on the preparation of octafluorocyclobutane(C4F8, RC318) has been carried out by the dimerization of tetrafluoroethylene(C2F4, TFE) in a mini-pilot plant. In order to control the reaction temperature during an exothermic dimerization of TFE, a cooling system was employed in the tubular reactor. The operating conditions have been established based on the continuous reaction in the mini-pilot plant. It was also found that the conversion of TFE and the selectivity of RC318 were greatly affected by the temperature, the pressure and the feeding rate of TFE.