Abstract: There is only a difference of double bond between cortisol and prednisolone.So it is difficult to separate them. When we use the silica column (0.26×25cm)with a dioxane/CHCl_3 eluent at flow rate of 1 ml/min, cortisol, prednisolone andanother impurities can be separated completely. The detection limit is 10~7--10~(-8)g.When EtOH/CH_2Cl_2 is used as the eluent, the detection limit is 10~(-9)g. A continuous flow radiodetector is used. The liquid scintillation solution isPPO, and the ratio of the column eluent and liquid scintillator is 1:4. The countsof ~3H--cortisol can be measured at an efficiency of about 30%. The detection li-mit is 10~(-8)Ci.