A fluidized reaction method for synthesizing propylene oxide by gas phase epoxidation of propylene and hydrogen peroxide relates to a microspherical alkali metal ion modified titanium silicalite zeolite TS-1 catalyst applicable to the reaction method, and a preparation method thereof. A gas-solid phase fluidized epoxidation method refers to a gas phase epoxidation method in which the raw materials of propylene and hydrogen peroxide are directly mixed in the gas phase under normal pressure and temperature above 100° C. and the feed gas enables the titanium silicalite zeolite TS-1 catalyst to be fluidized in an epoxidation reactor. A catalyst applicable to the reaction method is a microspherical alkali metal ion modified titanium silicalite zeolite TS-1 catalyst which has the main characteristic that alkali metal cations are reserved on the titanium silicalite zeolite.