Complement system is activated by three different ways - classical, alternative and lectin pathways. In presense of carbohydrate on the surface of microbes, manose-binding lectin (MBL) binds to members of the MBL-serine protease family (MASPI, MASP2 and MASP3) to generate proenzymes activating C4, C2, and C3 of complement system via the lectin and alternative pathways. However, these serine proteases have not been identified in pig yet. Therefore, this study was mainly focused on sequencing of cDNA and analyzing of structural protein of MASP1 molecule in pig. It was indicated that 3,009 nucleotide of MASP1, cDNA encoding 699 deduced amino acids was sequenced. The MASP1 gene had 16 exons and its encode polypeptide protein contained rich-cysteine domains such as CUB1 (a.a 18-138, 121 a.a, 2 cysteine), EGF _CA (a.a 139-182,44 a.a, 6 cysteine), CUB2 (a.a 185-297, 113 a.a, 4 cysteine) in N-terminus, two CPP domains (CCPI: a.a 301-362, 62 a.a, 4 cysteine and CCPa.a 367-432, 66 a.a, 4 cysteine) at the center ofprotein and Tryp_SPc domain (a. a 448-691, 244 a.a, 7 cysteine) in C-terminus. The putative signal peptide, N-glycosylation sites, catalytic sites and cysteines were also highly conserved between human and pig. Compared with human, porcine MASP1 showed 88 percent identity at protein level. Additionally, three single nucleotide polymorphisms at loci 1.650A -- G (Asp -- Gly, ex on 12), 1.748C --T (Leu -- Phe, exon 13) and 1.807C -- T (exon 13) were also found in a population of Landrace breed. This is valuable information for breeding program towards disease resistance in pigs.