Abstract: Objective Study on different growth environment and harvest time on the quality of Equisetum arvens L .To establish methods for identification and determination of Isoquercitrin in Equisetum arvens L. Method TLC was used to identify Isoquercitrin in Equisetum arvens L, and the content was determine by HPLC, Agilent ZORBAX SB-C18(4.6mm×250mm,5μm) column was used. Acetonitrile and 0.1% Formic acid water-solution were used as mobile phase of liner elution, and the volume flow was at 1.0mL/min; Ultraviolent determination wavelength was 354nm; and injection volume was 10μL.Results Different growth environment and harvest time influence obviously TLC and the content of Isoquercitrin. TLC spots were clear, and sparated nicely. the linear range of Isoquercitrin was 0.41μg/mL～95.13μg/mL; The average recovery in Equisetum arvens L was 97.2%. Conclusion June and August are the best harvest time . The method is believable for identitication and determination of Isoquercitrin in Equisetum arvens L. with its simplicity, sensibility, repeatability。