This study is on the biodegradability of the activated sludge, which used to biodegrade Linear Alkylbenzene Sulfonate(LAS), synthetic detergents and sufactants. The activated sludge in waste water treatment plant is used to the test of biodegradation of anionic surfactants and nonionic surfactants, but it have the periodic change of the biological propety to the lapse of the time. For the puropse of controlling and adjusting of the activated sludge in biodegradation test, we collected microorganisms from the sewage plant and the soil, and then, made the activated sludge in semicontinuous aeration chamber. From determined biodegradation data, and the degree of biodegradability to the LAS, we confirmd the standardized synthetic activated sludge which have more stable biodegradability than the sewage activated sludge. In continuous biodegradation test, LAS(dodecene-1) was biodegraded more than 99%, In 7days by the standardized activated sludge.