B1-grade high-fire-retardant low-smoke-generation rigid polyurethane foam

Disclosed is B1-grade high-fire-retardant low-smoke-generation rigid polyurethane foam which is good in fire retardant effect and low in combustion smoke generation. The foam is prepared by subjecting premixed polyether polyol and polymeric diphenylmethane diisocyanate (MDI) to mixing and foaming according to the weight part ratio of 1: (1-1.5), and the premixed polyether polyol is composed of the following raw materials of, by weight, 30-50 parts of phenolic resin polyol, 20-50 parts of polyether polyol A, 0-50 parts of polyether polyol B, 0-30 parts of polyester polyol C, 1.5-3.0 parts of an organosilicone foam stabilizer, 3.0-6.0 of a composite catalyst, 0-10 parts of a liquid fire retardant, 0.5-1.5 parts of water, 10-25 parts of a physical foaming agent and 7-25 pars of graphite slurries.