In this paper, we simulated the heat transfer and heat sealing processes of a lithium polymer battery package using finite element method (FEM). We observed and calculated the temperature change of an aluminum (Al) laminate thin film and sealing block during different sealing times. We also calculated the temperature change of the sealing block during consecutive heat sealing processes. For the design of the sealing block for the manufacturing process, we set the heat sealing time and area of the sealing block of the lithium polymer battery packaging as variables in heat transfer analysis. We succeeded in predicting effective heat transfer behavior and calculating the heat loss in consecutive heat sealing processes in numerical values.