The invention discloses an air purifying biological preparation and a preparation method thereof. The biological preparation of the invention is mainly composed of the following microorganisms by weight portions: 40-60 portions of rhodopseudomonas palustris, 10-30 portions of lactobacillus acidophilus, 10-30 portions of saccharomyces cerevisiae, and 10-30 portions of Jingyang streptomyces. The biological preparation of the invention contains multifold effective microbial floras, the beneficial microorganisms in the microbial inoculums can inhibit the effluvium components from being generated, on the other hand, the microorganisms act on the above components directly, thereby the content of harmful gases is reduced, the consistence of the effluvium is reduced, so that the biological preparation of the invention can quickly reduce the consistence of multifold harmful gases, such as ammonia, hydrogen sulfide, etc., can purify the air with notable deodorization effect, is applicable for deodorizing in culture farms, livestock houses, toilets, septic tanks, sewages, factories, odorous public places, sewage farms, etc.; in addition, the biological preparation of the invention can improve the immunity of the livestock, and can kill pathogen.