In order to investigate the mechanism of sodium arsenite inhibiting citric acid accumulation in citrus fruits, sodium arsenite solution(containing 6.16 g/L MgSO4?7H2O, 1 mL/L Triton X-100, 0.17 g/L NaAsO2) was applied by spraying onto ‘Yamashitabeni wase’(Citrus unshiu Marc), ‘Juxiangzao’(C. unshiu Marc) and ‘Dahongtiancheng’(C. sinensis Osbeck), as well as to detached juice sacs(MS medium containing 1.0 mg/L NaAsO2) and callus of ‘Bingtangcheng’(C. sinensis Osbeck)(MS medium containing 0.5 and 1.0 mg/L NaAsO2). The total soluble solid(TSS), citrate and malate contents, expression levels of CsAN1 and CsPH8 genes, and their promoter activities were analyzed. The results showed that NaAsO2 could reduce the citrate contents of fruit, juice sacs and callus tissues. After NaAsO2 treatment, the citrate contents of ‘Yamashitabeni wase’, ‘Juxiangzao’ and ‘Dahongtiancheng’ decreased by 4.59 to 61.57%, 0.67% to 14.92% and 13.22% to 54.35%, respectively, compared with CK group. CsAN1 and CsPH8 expression levels were significantly reduced under NaAsO2 treatment, with a 73% and 32% respectively decrease in ‘Juxiangzao’ fruit after 60 days of treatment, a 55% and 27% respectively decrease in ‘Bingtangcheng’ juice sacs after 21 days, and 73% and 84% respectively in the ‘Bingtangcheng’calli callus treated with 0.5 mg/L NaAsO2 for 20 days. The experiment under the absence of promoter subregions indicated that drought signals might act on the ABRE elements in the CsAN1 and CsPH8 promoters to regulate their expression, while the activity of promoter segments containing ABRE elements was significantly reduced after NaAsO2 treatment. It is speculated that NaAsO2 inhibits the activity of CsAN1 and CsPH8 promoters in citrus, thereby reducing their expression and weakening the accumulation of citric acid in the fruit.