[Objective] The applicability of different types of foaming agents and different bubble preparation methods in the preparation of foamed mixture lightweight soil of sludge(FMLSS) was studied in order to provide reference for environmental protection and utilization of river sludge.[Methods] From the micro and macro perspectives, different channels of silt and bubble mixed soil were investigated. The microscopic characteristics of different mixed soil of river silt and bubble was compared, and the influences of different microstructural characteristics on the physical and mechanical properties of various river silt mixed soil was anayzed.[Results] ① The microstructural differences of different types of river silt and bubble mixed soil were significantly affected by the amount of air bubbles and were less adffected by cement content. ② When the amount of air bubble was constant, the bubble would be burst seriously by hydrogen peroxide(H type), and the prepared soil with mixed river silt and bubble by hydrogen peroxide contained a small amount of big atmospheric pores and the distribution was uneven. Under the same density, the air pore content of H type river silt and bubble mixed soil was more, and the quality of the mud-bubble mixing soil was worse. ③ The distribution of FMLSS micro pores made by compound foaming agent(F type) and anionic foaming agent K₁₂A(K type) were better. But the pore size of F type foaming agent was small and the distribution was uniform and good strength and deformation characteristics were shown.[Conclusion] The first foaming process is better than the later foaming process. The F type foaming agent has better applicability in the preparation of foamed mixture lightweight soil using of river sludge.