The invention relates to the field of biological pesticides, in particular to a biocontrol inocula and a preparation method thereof. The raw material shrimp shell and squid cartilage are separately ground and dried, and passed through a 3-mm sieve, 3 kg of raw material shrimp shell and 1 kg of squid cartilage are weighed; a beef extract peptone liquid medium is used for fermentation of chitin-degrading bacterial actinomycetes 5 L and Bacillus spp 4 L, and the actinomycete is Streptomyces avermitilis (CGMCC 4.7296, Culture Collection of Chinese Academy of Sciences); and the Bacillus spp is Bacillus subtilis (CGMCC 1.821, Culture Collection of Chinese Academy of Sciences). The above two fermentation broths and a mixture of powdered shrimp shell and squid cartilage are added to a fermenter, and subjected to aeration fermentation at 80 DEG C for 30 days at 30 DEG C, 1 kg of fulvic acid is added, and the materials are uniformly mixed to obtain the biocontrol inocula.