Olefin polymerization catalyst, preparation method thereof and preparation method of polyethylene

The invention provides an olefin polymerization catalyst. The olefin polymerization catalyst comprises a carrier and a Ziegler-Natta catalyst carried by the carrier, wherein the carrier is a porous polymer microsphere, the pore size of the porous polymer microsphere is 10-25nm, and the Ziegler-Natta catalyst is carried by the porous polymer microsphere carrier with a pore size of 10-25nm to obtain the olefin polymerization catalyst. In the process of carrying out catalytic polymerization on ethylene by using the olefin polymerization catalyst, once generated, the PE (polyethylene) molecular chains are entangled mutually due to the specific pore size of the porous polymer microsphere, and the PE molecular chains are difficult to unentangle, thus the movement of the PE molecular chain is hindered, and the melting point is increased to the temperature of143 DEG C. The invention further provides a preparation method of the olefin polymerization catalyst and a preparation method of PE.