The present invention discloses a preparation method and application of Bacillus coagulans and a spore preparation cultured in high density, and belongs to the microbe technical field. A Bacillus coagulans strain is classified and named Bacillus coagulans JSSW-LA-07 and is preserved as CGMCC No.2602 in China General Microbiological Culture Collection Center. The Bacillus coagulans strain JSSW-LA-07 can produce spore under an aerobic condition and produce a small amount of L-lactic acid in the metabolism during a course of fermentation. The Bacillus coagulans strain can produce L-lactic acid with a higher purity under an anaerobic condition. The strain does not produce substances which can be harmful to human and cultured animals, has the characteristics of innocuity, on residue, no side effect and the like, has a great significance for production of green and safe livestock, fowls and marine products and improvement of cultivation ecological environment, and can be widely applied in the cultivation production of high yield, high quality, high efficiency, synusiologic and safe livestock, fowls and marine products, and the regulation and control of the ecological environment of cultivation.