Abstract:[Background] Compared with single microbial agent, microbial compound agent is more efficient and stable to promote crop growth. [Objective] To develop a microbial compound agent that can significantly promote the growth of rice, and build a mathematical model for the construction of microbial compound agent. [Methods] Bacillus amyloliquefaciens FH-1 was mixed with one of the seven plant growth promoting bacteria, in a biomass ratio of 1:1. The high-efficiency compound microbial agent was screened by rice pot experiment. Biochemical methods were used to determine the growth promoting characteristics of compound agent. Based on the analysis of the correlation between the plant characteristics and the growth promoting characteristics of the strains, a mathematical model for the construction of microbial compound agent was established by using the general linear equation. [Results] Compared with the control, microbial compound agent FN (Bacillus amyloliquefaciens FH-1 and Brevundimonas sp. NYM-3) significantly increased the rice shoot length, root length and fresh weight of rice by 20.79%, 26.67%, and 74.84% (P<0.05), respectively. The microbial compound agent FN was the best microbial compound agent among the seven microbial compound agents. Partial correlation analysis showed that the abilities to dissolve inorganic phosphorus, to produce siderophore and to secret ACC deaminase might play more important roles in promoting plant growth. According to the results of partial correlation between the plant growth promoting characteristics of microbial agents and the characteristics of plants, the mathematical model for the preparation of microbial compound agent was constructed and the prediction accuracy was over 97%. [Conclusion] We have successful developed a high-efficient microbial compound agent to promote rice growth, and constructed a mathematical model for the construction of microbial compound agent, which could provide scientific guidance for the development of the microbial compound agent.