The effects of arbuscular mycorrhizal fungi (AMF, Glomus mosseae) on plant dry weights, sucrose and glucose concentrations, and sucrose-metabolizing enzyme (AI-acid invertase; NI-neutral invertase; SS-sucrose synthase) activities were examined in young citrus (Citrus junos Sieb.ex Tanaka) seedlings. After three months of mycorrhizal inoculation, root mycorrhizal colonization was 55.32%. Inoculation with G. mosseae significantly increased shoot and root dry weights and sucrose and glucose concentrations in leaf and root, compared with non-AMF seedlings. AMF colonization was significantly positively correlated with glucose and sucrose concentrations of leaf and root, suggesting that AM symbosis alters carbohydrate concentrations to sustain symbiosis development. On the other hand, AMF colonization significantly increased root AI and leaf SS activities, but decreased leaf AI and NI activities and root NI and SS activities. Based on the correlation analysis, it assumes that AMF regulated the carbohydrate concentrations for the plant growth and mycorrhizal development through altering activities of the sucrose-metabolizing enzymes.