Abstract: By analyzing the experimental principle, scope of application and technique key points of the six classical test methods of ready biodegradability, it was pointed out that the test agency should select suited test method according to test substance characteristics. The 301A and 301E methods can only be applied to test substance which is soluble in water, non-volatile and non-adsorbable; the 301B method cannot be applied to test volatile substance; when the 301C, 301D and 301F methods are applied to test substance containing nitrogen, the oxygen consumption of nitrification should be corrected. After comparing the tested materials preliminary treatment, adding, apparatus, test operation and sampling requirements of the six test methods, it was indicates that the obtaining of valid test data needed design of appropriate test program and adoption of appropriate apparatus, and the effect of such factors as test water quality, dispersion,, apparatus on abnormal results and interference should be analyzed.