Abstract: The present invention belongs to the technical field of NMN preparation, and particularly relates to a recrystallization method for NMN preparation, comprising the following steps: step 1. preparation of raw materials: preparing nicotinamide, nucleic acid, ribose-5-phosphate and phosphoric acid; step 2. preparation of reaction solution: preparing a suitable buffer, dissolving nicotinamide, ribose, ribose-5-phosphate in the buffer, and adjusting the concentration of the solution; step 3. activated phosphorylation reaction: adding phosphoric acid to the buffer of the dissolved nicotinamide and ribose, and stirring the mixture at appropriate temperature and pH conditions to make reactions take place in the mixture; step 4. addition of enzyme for catalysis; step 5. separation and purification: separating and purifying the reacted mixture to remove unreacted substrates and synthetase.