To find out the relationship between macrophyte and bacteria, the numbers of free-living bacteria and attached bacteria in two macrophytes dominant ponds were estimated weekly from May to August, 1995. The free-living bacterial numbers and attached bacterial numbers removed from macrophytes with stomacher were measured by the Acridine Orange Direct Count method. The free-living bacterial numbers were ranged 0.3x10^6∼2.3×1066 cells·ml^-1, and those were not correlated to chlorophyll a concentration. The maximum peak were appeared at flowering period. The attached bacterial numbers on N. tetragona, N. indica and A. calamus were ranged 2.4×10^6∼16.4×10^6 cells ·cm^-2, 10.6×10^6∼101.5x10^6cells ·cm^-2 and 2.3×10^6∼14.5x10^6cells ·cm^-2, respectively. The attached bacterial numbers of same pond were different from each host macrophyte. Just after the flowering period of each macrophyte, the attached bacterial number had maximum, which means that the bacterial community was affeced by the life cycle of macrophytes.