NOVELTY - Antagonistic bacteria comprise Bacillus cereus strain X5 (CGMCC 4161) having main morphological characteristics comprising Gram-positive G+, movability, having adnate flagellum, rod shape, generating spores, ivory bacterial colony, round shape, irregular edge, and moist and smooth surface. It has physiology and biochemistry characteristics comprising catalase positive, Voges-Proskauer (VP) reaction negative, methyl red test positive, and indole test positive.    USE - Antagonist bacteria used in preparing microbial organic fertilizer for preventing tomato root-knot nematode (claimed).    ADVANTAGE - The microbial organic fertilizer makes antagonistic bacteria rapidly breed after being fertilized into soil, thus reducing root-knot disease index in continuous cropping soil with heavy root-knot nematode by 40%, egg mass of every strain by 68%, and amount of eggs of every egg mass by 58%. The exertion of microbial organic fertilizer effectively prevents harm of root-knot nematode.    DETAILED DESCRIPTION - Antagonistic bacteria comprise Bacillus cereus strain X5 (CGMCC 4161) having main morphological characteristics comprising Gram-positive G+, movability, having adnate flagellum, rod shape, generating spores, ivory bacterial colony, round shape, irregular edge, and moist and smooth surface. It has physiology and biochemistry characteristics comprising catalase positive, Voges-Proskauer (VP) reaction negative, methyl red test positive, indole test positive, and fermentation glucose, xylose, L-arabinose, mannitol acid production. It uses citrate, nitrate reductase positive, amylolysis positive, gelatin hydrolysis positive, decomposition casein positive, fat hydrolysis positive, and phenylalanine dehydrogenase test positive. An INDEPENDENT CLAIM is included for preparation of microbial organic fertilizer by inoculating antagonistic bacteria X5 to modified beef extract liquid culture medium to perform fermentation at pH of 6.8-7.5, culturing temperature at 30-35 degrees C, and stirring speed of 180-300 revolutions per minute; forming spores at middle or rear period of fermentation, such that content of bacteria or spores of antagonistic bacteria in fermentation liquid is greater than or equal to 1x 1010 cfu/ml; performing solid fermentation to antagonistic bacteria X5 fermentation liquid and mixture of rotten pig manure compost and vegetable dregs microbe zymolyte, such that every ton of solid organic material is added with 55 l of X5 fermentation liquid; mixing uniformly; turning pile once every day during solid fermentation so that solid fermentation temperature does not exceeds 50 degrees C; finishing after fermenting for 5 days so that content of antagonistic bacteria X5 reaches more than 1x 108 cfu/g; acquiring microbial organic fertilizer of antagonistic bacteria X5; drying microbial organic fertilizer at temperature lower than 60 degrees C until water content is 30%; and packaging microbial organic fertilizer.