Abstract: This article summarizes the application of ultrasonic wave in nucleation of organic systemssuch as sucrose, monosodium glutamate, glutamic acid, monohydrate α-glucose, etc. and analyzesits principle . The necessary nucleation conditions for isomers of allomorphic organic system under the effect of ultrasonic wave were obtained by studying glucose. When ultrasonic wave is used to promote nucleation of organic system supersaturate solution, a nucleation solvent is usually needed. The nucleation solvent for one isomer of allomorphic organic system should be favourable to separating out the isomer. The nucleation of amphoteric substance such as antibiotic and amino acid can be achieved by only applying ultrasonic wave at its isoelectric point or by using ultrasonic wave and nucleation solvent when the system viscosity is high.