Lipase hydrolyzes the substrate 6-methyl test halogen spirit ester in microemulsion solution in the presence of Co lipase and bile acid. The presence of lipase and bile acid inhibits the affection of other hydrolases and esterases, so this method can detect the activity of LPS reliably without the affection of serum matrix effect.When 6-methyl test halogen spirit ester was degraded to 6- methylresorufin, the increase of absorbance caused by the red dye is in direct proportion to the lipase activity in the sample.