Abstract: Three species have been found new to Hainan Province while investigating weeds. They are:Alternantheru pungens H. B. K. , native to South America; Boerhavia erecta Linn. , reported from the Pacific islands and Xisha archipelago of China; Lindernia procumbens(Krock. ) Philcox, reported from the mainland of China. The plants grow on the cultivated areas. Alternanthera pmgens H. B. K. and Lindernia procumbens (Krock. ) Philcox are weeds. Their occurrence in Hainan Province warrants further studying.