The invention relates to a method for increasing selective non-catalytic reduction (SNCR) denitration efficiency, and belongs to the field of control of nitrogen oxides. The method comprises a step of spraying natrolite powder in an SNCR system while spraying ammonia liquid, urea, ammonium hydrogen carbonate or ammonium carbonate serving as a reducing agent in the SNCR system; and thus, the utilization rate of the reducing agent of the SNCR system is increased by a sodium element and other trace elements such as nickel, titanium, vanadium, molybdenum, selenium and the like in the natrolite powder, the denitration efficiency is increased, the optimal reaction temperature range of the system is expanded, the oxidation reaction of the reducing agent and the nitrogen oxide is suppressed, the leakage of the reducing agent of the system is reduced, the consumption of the reducing agent of the SNCR system is reduced, and a basis is provided for application of the SNCR system under more working conditions.