Objective:To investigate the qualitative and quantitative change law of essential oil components in Citri Reticulatae Pericarpium（CRP） harvested in different time from the same plant.Method: The volatile oils were extracted by steam distillation and analyzed by GC-MS.The overlapped peaks were resolved by the programs of GC-MS data analysis and AMDIS.Result: A total of 72 compounds in the essential oils of four batches CRP were identified

which represented 95.542%

92.138%

98.655%

and 96.201% of the total relative content

respectively.The two compounds that have the highest content are limonene and linalool

accounting for 43.78-68.432% and 9.258-15.724% respectively.Quantitative changes of some compounds present regularity.Conclusion: The essential oil of each batch CRP has almost the same chemical constituents

whereas the relative content of each constituent shows some difference.The quantitative change law of some components may have important meaning to explore the dynamic change law of volatile oil components in CRP.The combined utilization of programs of GC-MS data analysis and AMDIS can efficiently solve the difficulty in the qualitative and quantitative analysis of overlapped peaks.