Abstract: The composite inocula used for green waste composting are usually liquid, its production requires rigorous aseptic conditions, and the products are inconvenient to transport. These problems are attempted to be solved by developing a solid microbial inoculum. Two strains of Bacillus sp. B01 and B02 were used as the components of the composite inoculum, the proportion and concentration of the strains were optimized using an orthogonal experiment to develop the solid composite inoculum (SB012), and the promotion effect of the solid composite inoculum on green waste composting was evaluated (compared to the relative liquid compound microbial inoculum (LB012)). The results showed that both factors had significant influences on the functions of the composite inoculum, and the proportion of B01 and B02 had greater influences than the concentration. The proportion (B01:B02) of 7.5:2.5, and concentration of 2.5% constituted the composite inoculum with the optimal functions. Compared with the LB012, the utilization of the inoculum in green waste composting process increased the lignin degradation rate by 7.79%, cellulose degradation rate by 5.30%, humus content by 6.29%, and humification coefficient by 23.02%. Generally, a solid composite inoculum called SB012 was developed by optimizing the proportion of B01 and B02 and their concentration. The application of the composite inoculum during green waste composting effectively degraded lignin and cellulose, promoted the synthesis of humus, and improved the quality of compost.