Abstract: Three bioassay methods for monitoring the resistance of Helicoverpa armigera Hübner to Bacillus Thuringiensis Insecticidal Proteins were evaluated, ie dose response and growth inhibition assays with the test material incorporatied in diet and leaf dipping method. The results showed that the mortality from diet incorporation mothod using second instar larva is more suitable for resistance monitoring,and the best time for morality investigation was 5 days after Bt formulation treatment and 14 days after Cry1Ac treatment. The mortality of untreated larvae can be controlled below 20% by using improved artificial diet. Resistance Ratios were 4.6,3.9 and 3.8 folds to Cry1Ac and 1.1,1.4 and 1.6 folds to Bt formulation with Qiuxian,Jizhou and Gaomi populations in 1998 compared with a laboratory population using the diet incorporation mortality method.