To develop a rapid and highly selective method for detection of citric acid is a must as citric acid is an important marker for a variety of diseases.A water soluble hydroxypyridine functionalized spiropyran probe was designed and synthesized by introducing hydroxypyridine group into spiropyran skeleton,as to improve its binding ability to citric acid through the synergy effect between spiropyran carbon and hydroxyl group.Results showed that the probe responded to citric acid with high selectivity,accompanying with significant color change and fluorescence quenching.Based on this,a rapid and sensitive fluorescence method for detection of citric acid was established.The probe was applied in the detection of citric acid in urine sample,with a linear range of 20-120 μmol/L and a detection limit of 1.0 μmol/L.Moreover,the probe was used for the detection of citric acid in 2.5% artificial urine.The recoveries ranged from 85.7% to 92.2%,with relation standard deviations of 3.0%-9.2%.The method is facile,accurate and selective,and is potential in the determination of citric acid in urine.