Abstract: The major chemical components of volatile oil in slash pine needles were first analyzed and identified by using quartz capillary gas chromatography and GC-MS. There were at least 33 components of monoterpene and sesquiterpene in the volatile oil, including 18 kinds of monoterpenes and 15 kinds of sesquiterpenes. High amount components in monoterpenes were α-pinene, β-pinene, lemonene and α-terpineol, and the contents of β-pinene got up more than 50% of toeal monoterpene contents. It was quite different from in trunck oleoresin that there were rich contents and compositions of sesquiterpene in needles. The relative contents of each component of monoterpenes and sesquiterPenes varied in different monthes. The monoterpene contents were 58. 7% of total contents of monoterpenes and sesquiterpenes in March, but in May monoterpenes just 39. 5% and sesquiterpenes up to 60%.