The invention discloses a method for synthesizing a P zeolite molecular sieve from rice husk. The method includes: subjecting crushed rice husk to pretreatment with sulfuric acid, conducting washing and drying, then putting the dried rice husk into a muffle furnace for pyrolysis, collecting combusted rice husk ash, putting the combusted rice husk ash and a sodium hydroxide aqueous solution in a high pressure kettle to conduct hydrothermal activation for 2-4h under a temperature of 180-230DEG C, and performing cooling to obtain an activated alkali solution, adding an aluminum source into the activated alkali solution, then adding a P zeolite molecular sieve crystal, and carrying out aging, heating crystallization, filtering, washing and drying, thus obtaining a finished product. The method realizes waste recycling, and has the advantages of simple process, short production period, easy operation, and the obtained product has the characteristics of high quality and low cost, etc.