Abstract: Changes in concentrations of free sugars(fructose, glucose and sucrose), myo-inositol and potassium (K) in the pulp during fruit development and maturation of citrus i.e. Kamei（seedless） Satsuma mandarin（Citrus unshiu Marc.） and Egan 1 (seedy) tangerine（Citrus reticulata Blanco）were investigated. The results showed as follows: (1)During the early phase of fruit enlargement, concentrations of fructose and glucose of Egan 1 obviously increased, that of sucrose showed little change, while myo-inositol concentration progressively decreased, during the middle and later phase of enlargement, sucrose concentration significantly increased, others changed slightly. Concentrations of fructose, glucose and sucrose of Kamei all markedly accumulated during the early and middle phase of fruit enlargement, myo-inositol concentrations were relatively stable except that the relatively small peak presented during the middle phase of enlargement. Changing trends of total sugars were almost accordant with those of sucrose in the pulp of two cultivars during fruit development. (2) During fruit storage, myo-inositol and total sugars of two citrus cultivars remained relatively constant, whereas concentrations of fructose, glucose and sucrose between two cultivars were all in the reversed trends.(3) K concentrations in the pulp of two cultivars significantly increased and remained relatively high levels during the stage of fruit enlargement.