In this paper,the single factor test was used to optimize the second derivatization conditions of isobutyl chloroformate,and a gas chromatography quantitative detection method for 18 free amino acids in citrus pulp was established. The results showed that the analysis conditions were the best when pyridine,2methyl1propanol,first isobutyl chloroformate and second isobutyl chloroformate were added in the amount of 20 μL,120 μL,50 μL and 50 μL,respectively,and the extraction solvent was dichloromethane. The 18 amino acids showed good linearities in their respective linear ranges,and the correlation coefficient R2 were greater than 0.99. The detection limits were in the range of 0.02-0.35 μg/mL,and the relative standard deviations of 5 repeated tests were no more than 10.57%. The recoveries in five kinds of citrus extracts were between 72.82% and 132.97%. The method is simple,accurate,reproducible,low in cost,stable in derivatives,which can be used for the detection of 18 free amino acids in citrus pulp.