Abstract: In order to deeply analyze the microstructure of silicate modified polyurethane grouting reinforcement materials for mining and understand the influence of microstructure on the macro strength, firstly, the main reactions and reaction processes involved in this system are deduced. Secondly, the phase distribution of the composite system is characterized by scanning electron microscopy（ＳＥＭ）. The enrichment state of elements is qualitatively characterized by surface scan method and the percentage of main elements and atoms in each phase is quantitatively characterized by point scan method. Finally, the influence of microstructure on the macro strength is studied. As a result, there are three phases in silicate modified polyurethane grouting reinforcement materials, which are polymer continuous phase, silica polymer microsphere phase and sodium carbonate acicular phase. The disordered distribution of phases in microstructure is easy to cause stress concentration, which is manifested in the decrease of mechanical strength of materials.