The ancient Chinese prescription Si-Miao-San (SMS), which is widely used for the treatment of various diseases, e.g. rheumatic disorders, has been modified (m1SMS, m2SMS). The purpose of this study was to investigate the anti-inflammatory, antioxidant, and anti-tyrosinase effects of Si-Miao-San, of its two modifications, the component herbs, and its main pure ingredients. In vitro tyrosinase, 2,2-diphenyl-1-picrylhydrazyl (DPPH), and lipid peroxidation (LPO) assays were carried out in order to determine the inhibitory potential of the samples. The traditionally applied decoctions as well as their fractions (n-hexane, DCM, n-BuOH) were tested for their activities in concentrations of 100 microg/mL and 400 microg/mL, and the pure compounds in a range 6.25 microg/mL to 100 microg/mL. In conclusion, the decoction of m2SMS exhibited strong antioxidant activity in the DPPH assay, while the decoction of the classical SMS formulation showed low activity. The present results have shown the modifications to be more efficient scavengers of free radicals, such as superoxide and peroxide radicals. In addition, the decoctions of the two modifications have been shown to be more potent tyrosinase inhibitors. These formulas may thus be used as antiinflammatory and anti-aging prescriptions, as they may help to prevent cell damage. This study clearly establishes the two modifications of Si-Miao-San as valuable sources of natural antioxidants and anti-inflammatory agents, and also as candidates in the search for modem pharmaceuticals.