Two kinds of two-dimensional axisymmetric models simulating the thermal sterilization process of pure water and 1.0% carboxymethylcellulose solution were established based on COMSOL Multiphysics software. The temperature changes simulated by different model at the same positions in the can were compared by wireless temperature sensor to verify the accuracy. The different performances of velocity field， temperature field and lethality field simulated by the two models were analyzed with 1.0% carboxymethylcellulose solution cans. The results showed that the model which considering the headspace could better characterize the physical field changes during liquid canned food sterilization. On this basis， the relative pressures in 1.0% carboxymethylcellulose cans at different headspace heights and different holding temperatures were analyzed by the model with the headspace. The higher the temperature was， the smaller the headspace height and the greater the relative pressure inside the cans became. Manufacturers could determine the pressure of different cans in each stage of the sterilization process to control the pressure of the sterilization tank and the maximum withstand pressure of the cans， so as to avoid the deformation of cans during sterilization.