The invention belongs to the fields of olefin polymerization catalyst carriers and catalysts thereof and olefin polymerization. A preparation method of a spherical catalyst carrier comprises the steps of: adding alcohol and magnesium halide in a mol ratio of 2-100:1 into a closed container, raising the temperature to 60-180 DEG C, stirring for reacting for 10min-6h; transferring the obtained solution to an inert solvent or a mixed system of the inert solvent and an emulsifying agent while the solution is hot, wherein the inert solvent or the mixed system of the inert solvent and the emulsifying agent has a temperature of -25 DEG C-30 DEG C and is in a flowing state; stirring, and washing 3-6 times with an organic solvent; and vacuum drying to obtain a solid spherical magnesium halide alcohol compound particle with small carrier particle diameter and uniform distribution, wherein the particle diameter of the carrier is 2 mu m-30 mu m. The carrier is dispersed into an organic solvent and reacts with a titanium halide compound at a temperature of -30 DEG C-30 DEG C to obtain a master catalyst. The master catalyst has spherical particles; and the titanium loading quantity (4.0-9.76 percent by weight) is high, the efficiency on catalyzing vinyl polymerization or propene polymerization or olefin polymerization by the catalyst is high and the average molecular weight of polyolefin can be adjusted between 15,000 and 9,000,000.