The present study investigated the effects of different temperatures (4℃,25℃ and 35℃) and pH (4.8,5.8 and 6.8) on citric acid content and related gene expression in satsuma mandarin (Citrus unshiu cv. Guoqing No.1) juice sacs under in vitro. The results showed that low-temperature increased the citric acid content in citrus juice sacs and decreased the expression of ACOs and ACLβ1. High-temperature had no significant influence on citric acid content,but increased the expression of CSs and ACLβ1,and decreased the expression of ACO1,ACO2,ACLα1,and CsPH8. Low pH had no significant effect on citric acid content but increased the expression of CSs,ACOs, and ACLs,while high pH treatment increased the citric acid content and CSs expression in citrus juice sacs,and decreased the expression of ACLα2. It is indicated that the effects of temperatures and pH on citric acid content in the in vitro culture system of citrus juice sacs is mainly related to the changes in the expression levels of genes for the synthesis and degradation of citric acid.