In order to optimize the best technical parameters in extracting tea caffeine by dichloromethane, the concentration of tea infusion, ratio of tea infusion and CH2Cl2, extracting standing time, shaking time, extracting temperature, pH value of tea infusion and extracting times were screened, then the main factors including ratio of tea infusion and CH2Cl2, shaking time, extracting standing time and extracting temperature were selected for orthogonal test, the results of which were checked again. The results showed that when mainly considering the yield rate of caffeine, the best parameters were as follows: tea infusion concentration of 10%, extracting temperature of 45 ℃, shaking time of 40 min, standing time of 80 min, ratio of tea infusion and CH2Cl2 of 1∶2.5, 2 times for extraction. Under this parameter condition, the yield rate of caffeine is 92.93%, the purity of caffeine is 39.58%; when mainly considering the purity of caffeine, the best parameters were as follows: tea infusion concentration of 10%, extracting temperature of 45 ℃, shaking time of 35 min, standing time of 100 min, ratio of tea infusion and CH2Cl2 of 1∶2.5, 2 times for extraction. Under this parameter condition, purity of caffeine is 43.37%, and the yield rate of caffeine is 85.13%.