Abstract: In order to screen microorganisms of degrading ammonia-nitrogen in culture pond,the strain 9A-7and 9A-19 were isolated from the shrimp-shellfish co-culture pond water of Rizhao by degrading ammonia-nitrogen via enrichment culture.The results of molecular biological,physiological and biochemical identification consistently showed that the strain of 9A-7 is Vibrio atypicus and the strain of 9A-19 is Vibrio diabolicus.The results showed that the ammonia degradation ability was related to the growth of the two isolated strains,whose correlation coefficient between the isolated strain cell density and ammonia removal rate is 0.916(9A-7) and 0.938(9A-19),respectively.The ability of degrading ammonia-nitrogen was significantly affected by salinity and pH of the culture solution and culture temperature,and the effect of salinity on ammonia removing rate of two strains was similar and the optimal salinity of both isolated strains was 30,however,the temperature has a less effect on the ammonia reduction rate of the strain 9A-7 than the strain 9A-19,and the weak alkalinity has more remarkable effect on that of the strain 9A-7 than the strain 9A-19.At salinity 30,pH 7.5,temperature 25 ℃,the ammonia reduction rate of the strains 9A-7 and 9A-19 was 90.67%, and 74.67%, respectively.The present results showed that the two isolated bacteria strains are ideal strains for removing ammonia of the culture water.