The invention provides a preparation method of 
nicotinamide mononucleotide. The preparation method comprises the following steps: carrying out 
phosphorylation reaction on raw materials containing 
nicotinamide nucleoside salt, 1, 8-bis (dimethylamino) 
naphthalene, 
phosphorus oxychloride and a 
solvent to obtain a reaction solution containing 
nicotinamide mononucleotide. On one hand, 1, 8-bis (dimethylamino) 
naphthalene can inhibit 
phosphorus oxychloride from continuously attacking 2-position or 3-position hydroxyl; on the other hand, one 
nitrogen atom of the 1, 8-bis (dimethylamino) is beneficial to removal of hydroxyl 
hydrogen at the position 2, the other 
nitrogen atom is beneficial to removal of 
chlorine in 
phosphoryl chloride, and removal of 
hydrogen chloride is facilitated under the synergistic effect of the two 
nitrogen atoms. Meanwhile, as the distance between two nitrogen atoms in the 1, 8-bis (dimethylamino) 
naphthalene is short, a transition intermediate formed in the process of removing 
hydrogen chloride from the 1, 8-bis (dimethylamino) naphthalene is more stable, so that the process of removing 
hydrogen chloride tends to 
intramolecular reaction, and the selectivity of 
phosphorylation reaction is further improved.