Unsaturated Polyester Resin (UPR) is widely used in areas such as construction, shipbuilding, automotive, chemical equipment, light industry products, and sports goods. However, these plastics are highly flammable, leading to frequent fires that cause immeasurable damage to both life and property. Hence, adding an appropriate amount of flame retardants to unsaturated polyester resin becomes crucial. Through the addition of composite flame retardants, extensive experiments were conducted to optimize the flame retardant and mechanical properties of unsaturated polyester resin after treatment. This expansion of fire retardant resin broadened its application scope.