Abstract: The soil enzyme activity and soil fertility in the invasive ragweed (Ambrosia artemisiifolia) and native weed (Digitaria chinensis) growing-plots were analyzed and compared by the same experimental garden methods. The results show that compared to non-vegetation and native-weed, the invasive ragweed significantly increases soil nutrient availability, especially, available K content in the invasive ragweed plots is 3.6 and 1.3 times of those in the non-vegetation and native weed plots, respectively. Compared to non-vegetation and native weed plots, the invasive ragweed plot has significantly higher activity of soil enzymes. In a conclusion, the invasive ragweed (A. artemisiifolia), has a more strong capacity to improve soil available fertility and activity of soil enzyme than the native weed (D. chinensis), which benefits its competition with native species.