In order to solve the problems of high entanglement and difficult processing of ultra-high molecular weight polyethylene (UHMWPE) prepared by traditional Ziegler Natta catalyst (Z-N catalyst), a magnesium dichloride supported Z-N catalyst cat1 (or cat2) was prepared by chemical reaction method using MgCl2, TiCl4, isooctanol, tetraethyl orthosilicate (or dihexyl phthalate) as the main raw materials.Low entanglement UHMWPE was prepared by slurry polymerization using cat1 and cat2 as the main catalysts and triethylaluminum as the co catalyst. The particle size distribution and metal element content of cat1 and cat2 were measured, and the effects of polymerization temperature and time on the catalytic activity of the catalyst and the viscosity relative molecular weight (Mv) of UHMWPE were investigated.The degree of entanglement of UHMWPE were characterized by rheological analysis and DSC thermodynamic annealing.The results showed that the prepared cat1 and cat2 were consistent with the initial design. Under the optimized slurry polymerization process, when the polymerization reaction temperature was 65 °C and 70 °C, the catalytic activity of cat1 and cat2 reached 27700 and 37700 g PE/g cat respectively. The Mv of the prepared UHMWPE was 6.01 × 106 and 5.03 × 106, and the initial storage modulus was 0.21 and 0.13 MPa respectively. The entanglement degree was lower than that of commercial UHMWPE.