Abstract: To discover genes differently expressed between lactation periods, suppression subtractive hybridization method was employed to construct a cDNA library expressed in mammary gland of 60^th but not or little in 28^th. Serum amyloid A protein was one of the positive clones which was verified by Real-time PCR. Moreover the gene was cloned by RT-PCR and the sequence was analyzed. Results showed that a differently expressed library was successfully created in mammary gland of 60^th lactation. The goat mammary gland SAA3 complementary DNA has an open reading frame of 396 nucleotides encoding a putative protein of 131 amino acids, the GenBank number was DQ839400. The homologies of nucleotide and peptide sequence of Xinong Saanen goat mammary gland SAA3 with bovine（NM_181016）, rabbit （M64696. 1）, human（BCA）20795） and mouse＇s（NM_011315） are 95%, 84. 3%, 81.3% and 81.9% and 93%, 76%, 72% and 72% respectively. The 27 nucleotides in goat SAA3 261-287 were deleted in that of human, rabbit, and mouse. There were six conserved domains longer than 5 amino acids in the amino acids sequences among them. Goat SAA3 had three additional potential binding motifs compared to human＇s.