Abstract: Fluoride in plant samples were determined by improved combustion hydrolysision selective electrode method. Deionized water was substituted of NaOH solution as absorption liquid and standard solution addition method was used for calibration, which obviously simplified the operation and reduced the determination errors. The detection limit of method for fluoride is 0.45 μg/g and the recovery is 90.2％～109.7％. The improved method has been applied to the determination of trace fluoride in plant samples and the results are in agreement with those from ion chromatography method.