The invention belongs to the field of preparation of molecular sieve material, and discloses a synthesis method of a titanium silicalite TS-1. The method is characterized by comprising the following steps of: preparing a titanium-silicon gel with a silicon source, a titanium source, a template agent, an alkaline mineralizing agent and water according to certain proportion, and introducing right amount of alkali metal salt in the gel preparation process through a direction method or an indirection method; then, executing hydrothermal crystallization at 160-180 DEG C; and obtaining the titanium silicalite TS-1 after filtering, washing, drying and roasting. With the synthesis method provided by the invention, depolymerization of the silicon source can be promoted in the gel preparation process, so that titanium can enter into a skeleton smoothly and generation of amorphous six-coordinate non-skeleton titanium can be restrained. Based on the action of alkaline metal ions and an acid site of the molecular sieve non-skeleton titanium, the acid site of the cheap titanium silicalite TS-1 is removed, and selectivity of propylene epoxide is greatly improved while taking the titanium silicalite TS-1 as the catalyst for the propylene epoxidation.