To establish a HPLC method to determine the content of aucubin in Eucommia ulmoides seeds,to search for the formation and accumulation of aucubin in Eucommia ulmoides seeds,and to provide foundation for the suitable harvest season of aucubin in Eucommia ulmoides seeds,the Hypersil GLOD-C18 column(250 mm×4.6 mm,5μm)with temperature at 25 ℃ was used.The mobile phase was methanol-water(8∶92),at a flow rate of 1.0 mL·min-1,and the detective wavelength was 206 nm.The results indicated that the method of HPLC was efficient,and the average recovery of the aucubin in Eucommia ulmoides seeds was 98.61%,RSD=1.14%(n=6).The determination of aucubin was gradually raised with the seed growth,while the formation and accumulation from June 25th to September 5th increased slowly,and the determination of aucubin from September 5th to 25th raised quickily,and then kept relatively stable.Considering the extraction and utilization of aucubin,the date from September 25th to October 25th was the most suitable period for collecting Eucommia ulmoides seeds.