An alkali metal ion modified titanium silicalite zeolite TS-1 for gas phase epoxidation of propylene and hydrogen peroxide and a preparation method thereof. The method includes: 1: preparing an alkali metal hydroxide modification solution containing a small amount of TPA+ ions; 2: conducting a controlled hydrothermal treatment on a TS-1 zeolite matrix by using the alkali metal hydroxide solution containing a small amount of TPA+ ions; and 3: conducting post-treatment on the hydrothermally modified TS-1 zeolite. In the washing process, the modified TS-1 zeolite wet material is washed with a low concentration alkali metal hydroxide solution; and alkali metal ions are reserved on the silicon hydroxyl of the modified titanium silicalite zeolite. The prepared alkali metal ion modified titanium silicalite zeolite has significantly improved catalytic performance in the gas phase epoxidation of propylene and hydrogen peroxide.