The invention discloses a synthesis method of a
lorcaserin derivative. The synthesis method comprises the following steps: resolving a compound shown as a formula (II) under the action of an optical resolving agent; performing post-treatment to obtain the
lorcaserin derivative. In the formula (II), R is H,
alkyl with 1-4 carbon atoms,
halogen, methoxyl or
nitryl; R2 is H,
alkyl with 1-4 carbon atoms, methoxyl,
carboxybenzyl, t-butyloxycarboryl, methylsulfonyl,
tosyl and substituted or unsubstituted benzyl; the optical resolving agent is acyl-substituted
tartaric acid. The revolving efficiency is increased by selecting the optical resolving agent having a specific structure, and an optical pure product of which the ee value is over 99 percent can be obtained by means of simple recrystallization; meanwhile, resolving operation is easy, a single
solvent is used for resolving, materials are fed into one pot, and the method is suitable for industrial production. The invention further discloses a synthesis method of a salt of the
lorcaserin derivative. The obtained salt of the lorcaserin derivative can be applied to preparation of novel weight-reducing medicaments.