Abstract: The gas volumetric method for determination of silicon was improved by adding a thermostat system and a cylinder weighing container to the detection system and enlarging the range of the gas measuring tube. The best alkalinity was 65 mL of 200 g·L-1 NaOH solution, and the react time was 1 h. The method was applied for analysis of silicon samples, giving RSD′s (n=6) and deviation in the ranges of 0.32%-0.47% and -0.45%-0.40%, respectively.