From September 2005 to October 2005,researches of water quality improvement and the algal control by biological methods were studied in three enclosures(area: 49m²;depth:1.5m) at Lianhua Lake.The 1# enclosure was the control,the 2# enclosure was treated with Wolffia arrhiza,the 3# enclosure was treated with Schizosaccharomyces sp and Rhodospirillum sp.The amount of Wolffia arrhiza was 300L×5×103L^-1 in 2# enclosure,and the amount of Schizosaccharomyces(300L×4×10⁵L^-1) and Rhodospirillum(300L×8×10⁸L^-1) was in 3# enclosure.Aerf thirty days,compared to the control enclosure,TP declined to 40% and 16%;the chla content reduced 51% and 31%;transparency increased to 87 cm and 55 cm;pH decreased 1.09 and 0.69 in the 2# and 3# enclosure,respectively.The results showed that the water quality can be improved and the growth of algae was inhibited by Wolffia arrhiza,Schizosaccharomyces and Rhodospirillum.