Abstract:Different methods of flowering regulation were used on oval Kumquat (Fortunella margarita Swingle), Ponkan (Citrus reticulata Blanco‘ Pokon‘ ) and Satsuma orange (C.reticulata Blanco‘ Miyagawa Wase‘) trees which were all grafted on rootstocks of trifoliate orange (Poncirous trifoliata) The changes in protein fractions during the flower initiation were determined by SDS-PAGE and IEF-PAGE. The results showed that flower numbers were obviously increased by girdling treatment and decreased by GA3, and were also decreased by BA treated at the early stage of flower induction but increased by that at the late stage of flower formation. At the flower induction stage, some of the special proteins were observed in the buds treated with GA3, but disappeared finally. In the flower primordium formation stage, the intensity of protein bands in the flower buds increased in the shoots girdled, and some special proteins were found in the flower buds. It is suggested that different methods of flowering regulation might result in different gene expression and characteristics of protein metabolism. Some protein with smaller molecules and lower isoelectric point were related to flower initiation of citrus trees.