The invention discloses a bioorganic fertilizer with disease preventing and growth promoting functions, and a preparation method thereof. The bioorganic fertilizer with disease preventing and growth promoting functions comprises a functional bacterium and a bioorganic fertilizer, and the functional bacterium accounts for 0.2-0.5% of the total weight of the bioorganic fertilizer with disease preventing and growth promoting functions; and the functional bacterium is Bacillus amyloliquefaciens. The preparation method comprises the following steps: 1, fermenting and decomposing an organic fertilizer; 2, adding the functional bacterium: adding functional bacterium powder to the organic fertilizer after the fermentation of the organic fertilizer is completed, and performing uniform mixing; and 3, screening and packaging a mixture prepared in step 2 to obtain the finished product. Compared with conventional organic fertilizers, the bioorganic fertilizer with disease preventing and growth promoting functions facilitates soil improvement and crop growth by using the dynamic decomposition of the microorganism through adding Bacillus with disease resistance, growth promotion, broad spectrum and bacteriostasis functions. The functional strain can be colonized in soil surrounding the rhizosphere in the fertilization process, and can effectively activate nutrients in soil, promote the earlygrowth and quick tillering and enhance the growth vigor of crops under the synergistic effect of organic components.