Abstract: To establish a method conversion between HPLC and UHPLC for determination of three main components(ephedra, baicalin, and phillyrin) in Xiao'er Feire Kechuan Keli. According to the regulations on HPLC to UHPLC conversion in section 0512 of the 2020 Pharmacopoeia Part IV General Principles, compliance conversion was carried out. Under the UHPLC method, the linear relationship of ephedra, baicalin, and phillyrin was good, with a correlation coefficient (r) ≥ 0.999 and the recovery between 95% and 100%. The methodological validation results met the acceptance criteria, and the determination results were basically consistent with HPLC. Compared with conventional HPLC methods, the UHPLC method can significantly shorten analysis time, improve analysis efficiency, and consume less solvent, make environmentally friendly.