IEF-SDS-PAGE(isoelectric focusing electrophoresis-sodium dodecyl sulfate-polyacrylamigel electro-phoresis)technique was applied to comparing and analyzing the changes in protein component during embryo differentiation and development of longan (Dimocarpus longan Lout.CV.Wulongling).The results showed that major components of proteins were generally similar at different development stages,but some changes also took place. The 7 new specific proteins were observed at different stages of the embryo development.They were TE1(27.1 kD,pI 7.3),TE2(17.5 kD,pI 8.2)on 38 days after anthesis(DAA);TE3(11.4 kD,pI7.6),TE4(13.2 kD, pl 9.9)on 45 DAA;TE5(22.6 kD,pI 7.2),TE6(18.6 kD,pI 8.3),TE7(23.5 kD,pI 3.6)on 52 DAA.These specific proteins showed good repeatability in the experiments. The number of protein points were comparatively higher on 31 DAA gel electrophoretogram. which indicated that rich synthesis and accumulation of proteins appeared at the stage of 31 DAA, and coincided with the results of the protein contents determined. The appearance or disappearance of the specific proteins might play an important role in longan’s embryo differentiation and development.