【Aim】 This study aimed to test the allelopathic effect of the water extract of the invasive plant Daucus carota L. on four plant species. 【Method】 The effects of water extracts from roots, stems, and leaves of D. carota L. at different concentrations (0, 10, 20, 30, and 40 g·L^-1) on the seed germination of four species were observed and recorded by using the method of filter paper in the culture dish. The allelopathic effects of the water extracts of D. carota L. were analyzed according to the allelopathic comprehensive effect index. 【Result】 The extracts from different parts of D. carota L. had certain effects on the germination rate, germination potential, germination index, vigor index, root length, and shoot length of the recipient seeds. Moreover, synthetic effects of allelopathic index showed that with the increase of the concentration of the water extract from the roots, stems, and leaves of D. carota L., the allelopathy inhibition to Trrifolium repens L., Lolium perenne L., and Agrostis matsumurae L. increased. The allelopathic effect to Festuca arundinacea L. was a double effect of "low promotion and high inhibition". The order of tolerance for the four turf grasses was F. arundinacea L. > L. perenne L. > A. matsumurae L. > T. repens L., and the allelopathic effect of the leaf extract from D. carota L. on these species was stronger than that of the roots and stems. 【Conclusion】 The allelopathic effect of the extract of D. carota L. on the 4 plant species is significant. Species with strong tolerance can be used for revegetation in serious invasion areas.