Synthesis method of hydroxyl capped polydimethylsiloxane

The invention relates to a synthesis method of hydroxyl capped polydimethylsiloxane. The method comprises the steps of taking dimethyl hydrolysate with the viscosity of 30-50CS and toroidal content of 20-30% as an end capping reagent, taking dimethyl cyclosiloxane (DMC) as a raw material, taking silanol potassium as a catalyst, and synthesizing hydroxyl capped polydimethylsiloxane with the viscosity of 10000-600000CS at 120-170 DEG C, wherein the use amount of the catalyst is 10-50ppm. Hydroxyl capped polydimethylsiloxane can be used for preparing adhesives, potting compounds, sealants and the like for electric and electronic devices. According to the method, the preparation process is simple, the viscosity is accurate to control, the polymerization time is short, the production efficiency is high, and the molecular weight distribution of a product is narrow.