The seasonal variation of two flavonoid, quercitrin and afzelin, in the leaves of Cedrela sinensis A. Juss. from May until November was investigated by high performance liquid chromatography. Separation by reversed phase chromatography on ${mu}-Bondapak;C_{18}$ column was achieved by isocratic elution. The concentration of quercitrin was 5.81% (w/w) in May and high in July(8.89%, w/w), August(7.94%, w/w), and decreased from September to November. The content of another flavonoid, afzelin was 0.06% (w/w) in May and highest in June (0.12%, w/w), and was reduced from July.