The invention provides a preparation method of a catalyst for olefin epoxidation reaction. The preparation method comprises the steps of preparing a mixture containing a titanium silicalite molecular sieve, a binder source, an alkaline earth metal oxide and water, molding the mixture to obtain a molded body, and drying and roasting the molded body, wherein the binder source is at least one selected from silica sol, silane with at least two hydrolysable groups and siloxane with at least two hydrolysable groups, and the weight ratio of the titanium silicalite molecular sieve to the binder source measured by SiO2 to the alkaline earth metal oxide to the water in the mixture is (70-98): (1.5-40): (0.05-25): (5-50). The invention also provides an olefin epoxidation method. The catalyst prepared by using the method provided by the invention has high hydrogen peroxide conversion rate and epoxide selectivity in olefin epoxidation reaction.