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[Objective] The purpose of this study was to investigate the allelopathy of aboveground/underground extracts of sweet potato（Ipomoea batatas）, and to control weeds in farmland from the perspective of plant allelopathy. [Method] Based on seed germination rate, root length, stem length, and biomass, the allelopathic effects of four solvent extracts（petroleum ether, ethyl acetate, n-butanol alcohol, and aqueous phase） from aboveground/underground parts of sweet potato on seed germination and seedling growth of three noxious weeds（Digitaria sanguinalis, Lolium multiflorum and Bidens pilosa） were examined in the laboratory. [Result] Four extracts（petroleum ether, ethyl acetate, n-butanol alcohol, and aqueous phase） had certain inhibitory effects on seed germination rate, root length, stem length, and biomass of D. sanguinalis, L. multiflorum and B. pilosa. Petroleum ether phase and ethyl acetate phase had the strongest inhibition on seed germination and seedling growth of D. sanguinalis, L. multiflorum and B. pilosa at concentrations of 1.00-2.00 mg/mL, the inhibition rates were 40%-100% and 50-100% for seed germination, 48%-100% and 66%-100% for stem length, 65%-100% and 67%-100% for root length, and 76%-100% and 75%-100% for biomass, respectively. The lowest inhibition extracts on seed germination and seedling growth of D. sanguinalis, L. multiflorum and B. pilosa were aqueous phase and n-butanol alcohol phase that showed a ‘low-promotion and high-inhibition effect’ on root length, stem length and biomass of these three weeds. With increasing concentration of four extracts, the inhibition rates of seed germination and seedling growth of D. sanguinalis, L. multiflorum and B. pilosa were gradually increased, and the overall inhibition rates followed the order biomass>root length>stem length>seed germination. Compared to synthetical allelopathic index of four extracts on D. sanguinalis, L. multiflorum and B. pilosa, the inhibition rates of ethyl acetate phase and petroleum ether phase of underground part of sweet potato were generally higher than those of aboveground part, while the suppression rates of aqueous phase and n-butanol phase of aboveground part of sweet potato were higher than those of underground part; and B. pilosa had the strongest inhibition, followed by D. sanguinalis and L. multiflorum. [Conclusion] The results of this study confirmed that the allelochemicals with main effect were in ethyl acetate phase and petroleum ether phase of sweet potato extracts, which provided an important for further identification of allelochemicals in sweet potato germplasm resources [ABSTRACT FROM AUTHOR]