Abstract: Propylenc was oligomerized by the complex catalyst prepared in situ from the nickel salt of 1, 1, 1,5,5,5-hexafluoropentane-2,4-dione and diisobutyl aluminum hydride.The linearity of the propylene dimers is in the range of 75-80%.It was observed that the Al/Ni (Molar ratio) value and the reaction temperature exerted evident influence on the activity of the catalyst and the linearity of propylene dimers.The reaction mechanism of the catalyst system has been discussed preliminarily.