An antimicrobial substance produced by Brevibacillus laterosporus isolated from the sea sediment was purified and characterized. The antimicrobial substance was purified by ultrafiltration, DEAE-Sepharose Fast flow chromatography, CM-Sepharose Fast flow chromatography and HPLC reversed phase column chromatography, and after the final purification step, one active fraction was obtained, designated R-1. The molecular weight (MW) was accurately determined by MALDI-TOF-MS as 1608.023 Da. And its pI was determined with Rotofor Cell BIO-RAD to be 8.55. Amino acid analysis of the purified R-1 showed that it was composed of Leu, Tyr, Val, Ile, Lys, Gly, Met, Ser and Ala. Most of them were hydrophobic and neutral amino acid except Lys which was a basic amino acid. And this accorded with pI of R-1. R-1 remained active over a wide temperature range and it also was active over a broad pH rang. R-1 was insusceptible to pancreatin, pepsin and alkaline proteinase. Agar radial diffusion assay showed that R-1 had low minimun bactericidal concentration against Gram-Positive Bacteria such as Streptococcus mutans, Staphylococcus aureaus, Clostridium and Gram- egative Bacteria such as Escherichia coli Pseudomonas putrefaciens And R-1 had antibacterial activities against Candida albicans