An analytical method for the detection of volatile fatty acids(VFAs) was established.Acetic acid(AA)，propionic acid(PA)，butyric acid(BA)，iso-butyric acid(iso-BA)，valeric acid(VA) and iso-valeric acid(iso-VA) were chosen as the target，and a dynamic solid phase microextration(SPME) device was developed.The effects of extraction materials，extraction time，extraction temperature，extraction flow rate,extraction temperature and time of desorption were investigated on the efficiency of SPME extraction，and by which the optimal extraction conditions were determined.Furthermore，test conditions for gas chromatography were optimized,and a new dynamic SPME method was developed for gas chromatography ionization detection(GC-FID) to determine VFAs with the detection limits of 1.0-4.7 μg/L.The RSDs for three replicate extractions ranged from 1.1% to 6.8%，and the calibration curves were linear in the four orders of magnitude, with correlation coefficients(r2) more than 0.990.The developed method was successfully applied in the determination of trace VFAs in the environment.