Abstract: OBJECTIVE To assess Dendrobium candidum water extract and soybean isoflavone's synergistic antioxidative function. METHODS According to method for assessment of antioxidant function which from the book of Technical Standards Testing& Assessment of Health Food (2003) and Jin's formula to assess Dendrobium candidum water extract and soybean isoflavone's synergistic antioxidative function. RESULTS Dendrobium candidum water extract,soybean isoflavone and Dendrobium candidum water extract combined with soybean isoflavone can't enhance the SOD activity in the red cells of the mice respectively(P>0.05),but Dendrobium candidum water extract combined with soybean isoflavone can enhance the SOD activity and lower the MDA concentration in the liver tissue of the mice significantly.Moreover, for enhancing SOD activity in the liver tissue, the Jin's Q value had reached 1.44. CONCLUSION Dendrobium candidum water extract combined with soybean isoflavone has synergistic antioxidative function.