Abstract: Through the engineering examples of the maintenance and upkeep project of the Chen Family Ancestral Hall, this paper summarizes and studies the traditional gray plastic process in Lingnan. By improving the formula of the gray plastic material, dry rice straw, jade buckle paper and other materials are added to the lime slurry to prevent the cold shrinkage and heat expansion of the gray plastic, enhance the toughness of the gray plastic, and enable it to achieve functions such as moisture absorption, waterproofing, moisture absorption, sterilization, mold prevention, and air purification. It effectively solves the shortcomings of traditional gray plastic, such as easy fading and damage, fast surface peeling rate, and low cost, simple construction, and relatively low production requirements. The inheritance and development of traditional gray plastic craftsmanship in Lingnan ancient architecture have high practical value and promotional significance.