Abstract: This article introduces the current usage status of an existing hospital, and studies the BIM design, as well as the decoration technology of the prefabricated partition wall system, prefabricated floor system, wall body quick installation wall panel system, integrated ceiling system, and integrated squatting toilet system used in the secondary decoration and renovation of the public restroom in the existing hospital. By integrating and applying the technology of each prefabricated decoration system, the goal of high-quality, efficient, green, and environmentally friendly renovation of the public restroom in the existing building has been achieved. By comparing with traditional decoration techniques, the vitality and role of prefabricated decoration technology in the renovation of existing buildings are highlighted, providing useful references for the future renovation of existing buildings.