In order to screen the strains which have the capability of reducing the citric acid, 15 strains of yeasts were isolated from the materials of waste water and waste residue. The waste water and residue were collected in the citric acid factory. The yeasts were screened based on the capability of fermenting the citric acid. It was found that the 5 strains had good capability of reducing the citric acid. They could reduce at least 70% citric acid of the culture medium after 5 d fermentation. The 5 strains were tested the stress resistance of ethanol. The strain NS2 and NL2 have strong stress resistance. The morphological and physiology characteristics of NS2 and NL2 were measured by microscopic observation, assimilation of carbon and nitrogen. Then the two strains were identified by 18S rDNA sequencing and the phylogenetic analysis. In the end, NS2 was identified as Pichia kudriavzevii, NL2 was identified as Candida tropicalis. They can be used in the technology of acid reduction in the hawthorn wine in the future.