Abstract: Silicon tetrafluoride gas could be prepared by the pyrolysis from phosphate fertilizer by-product sodium fluorosilicate.This method produced no waste，and had lower production cost and a broad development prospect.A series of static experiments were carried out to investigate various factors that affect the pyrolysis of sodium fluosilicate.It was found that the optimum reaction temperature of sodium fluosilicate pyrolysis should be maintained in the intermediate temperature region （500~700 ℃），and the reaction pressure was maintained at atmospheric pressure or slightly negative pressure state.The production of silicon tetrafluoride gas with this method had the characteristics of high purity and no by-products.

Key words: sodium fluosilicate, silicon tetrafluoride, pyrolysis, static experiment