During the charging and discharging process of lithium battery, internal expansion will occur in lithium battery. In order to better understand the pressure of expansion on lithium battery pack, PF pressure color film must be used to provide reference for its pressure. PF pressure film can clearly show the pressure distribution between lithium battery packs, providing R&D engineers with better solutions to defects in the battery design process and production engineering, such as coating uniformity and pressure uniformity of steel roller.