To investigate the structure and function of MSG1 gene of Mycoplasma suis, a 1 011 bp gene MSG1 was cloned using nested PCR and a phylogenetic tree was constructed, bioinformatics analysis was hence studied. From the results of phylogenetic tree showed that the Mycoplasma suis was the most homogeneous to the Mycoplasma parvum, and from the results of bioinformatics analysis showed that the sequence encoded 336 amino acids. Its isoelectric point and molecular weight were 6 210 and 36 745.8 respectively, and the protein had no signal peptide and transmembrane region, and had higher antigen index and immunogenicity. The protein had lots of flexible regions, and its 3D structure presented as capital letter X, the peripheral structure was looser.