Abstract: Provided are a porous silicone resin and a light-weight flexible flame-retardant composite material, belonging to the technical field of nano-porous materials. The porous silicon resin is prepared from a porous silicon resin precursor solution by means of curing and drying processes. The porous silicone resin precursor solution includes a flame retardant, a surfactant, a siloxane monomer, a catalyst, an auxiliary agent and a solvent. The porous silicone resin precursor solution is obtained by firstly dissolving the flame retardant and the surfactant in the solvent, and then adding the siloxane monomer, the catalyst and the auxiliary agent and mixing them uniformly. The porous silicone resin and the light-weight flexible flame-retardant composite material prepared therefrom have the excellent properties of high porosity, high flame retardancy, high elasticity and high strain.