From the flowers of Hemisteptia lyrata Bunge, two flavonoids, apigenin (1) and acacetin (2), were isolated. Their structures were established by UV, one- and two-dimensional NMR, and mass spectroscopic methods. Apigenin showed significant inhibition against mushroom tyrosinase with an IC_50 value of 4.56㎍·ml^-1, and appeared to inhibit the polyphenol oxidase activity of tyrosinase in a competitive manner (K_1=2.5×10 exp (-5) M) when L-tyrosine was used as a substrate, but did not inhibit the melanin production of Streptomyces bikiniensis.