The invention relates to a biotechnology dealing agricultural discard stem with an highly effective stem decomposing composite bacterial, which dissolves the problem of single species of applying microbiological bacterial, weak breaking up, low total degradability rate of cellulose, long developmental cycle. The composite bacterial comprises the following parts: yellow archespore wool bacterium leather bacterial, mushroom bacterial, haci trichoderma, green trichoderma, coninic trichoderma, aspergillus niger, bacillus subtilis, feed bacillus, bacillus megaterium, candida, distillery yeast, food-yeast, brown sphere azotobacter, thermoactinomyces, and so on. The composite bacterial can overall degrade lignin, cellulose, hemicellulose and other organic material in the stem, has a more than 80% degrading rate, a 10-15 days short cycle, keeps a long time for providing a solid bacteria.