Abstract: By using indoor biological simulation test (an auxiliary means to determine environmental parameters), effects of different phosphorous in four domestic detergents on S.obliquus Ktz growth were examined to judge the phosphorous ban measure. Phosphoric concentrations of the tested detergents were between 0.05 and 5.0 mg/L according to the monitoring data of D watershed which is drinking water source for Shenzhen City,China S.obliquus Ktz growth tests were conducted in an environment with sole phosphorous of detergents. The results showed that domestic detergents of various types significantly promoted the growth of S.obliquus. Algal density exceeded the universal state and international standards of 7.5?05-1.0?06 ind/L for eutrophication assessment. Under the conditions of daily ordinary consumption of high P washing powder, the biomass of algal would be up to 6.2?09 ind/L, almost 60%higher than than the algel biomass while using low P washing liquid. During the whole experiment,The growth rate of S.obliquus in the contrast group of non-phosphorus never exceeded the experimental group Contaring highlevel phosphorus. As a basic element necessary for S.obliquus growth, the increase of phosphorus can result in the increase in S.obliquus density. algal potential growth would be great with P existence. Therefore, limit the input of phosphorus from detergents, reducing the nutrient supply, lowing the nutrient concentration of water,can help to control the eutrophication of waterbodies.