A method of preparation of silyl derivative of sarmentosine and its gas-ohromatographio determination are described.The sample for analysis is treated.with a mixture of BSA and TMCS in 5:2-V/V ratio at 60℃ for an hour to effect quantitative silylation,while the application of other silylating reagents such as HMDS and TMCS was unsuccessful.The silyl dexivative obtained from the extract is analyzed on a column of XE-60 at 200℃.The result is qualitatively in agreement with that obtained from thin layer chromatogxaphy.However the GC method is simple,more rapid and accurate,the standard error is within the range of ±2.1%.