Abstract: At present，polyurethane and sodium silicate modified polyurethane are the most widely used grouting reinforcement materials in coal mine，but the latter has gradually become the most widely used advanced grouting reinforcement material due to the advantages of non-combustion and low reaction temperature. As one of the most widely used coal face grouting materials，its performance stability is very important. In the actual grouting，the phenomenon of white material layering in two components often occurs. In order to achieve the expected reinforcement effect and ensure the construction safety. In this paper，the influence of key parameters in water glass on the stability of white material system，such as modulus，Baume degree and iron ion content are studied. The precipitation amount of component a under different parameters was recorded，and the content of iron ion in the sample was determined by spectrophotometry. In addition，the main components of the precipitates were analyzed by FTIR. The results show that 3.3 high modulus sodium silicate easily leads to gel formation. The 2.4-2.7 modulus has little effect on the precipitation of the system，which eventually leads to the precipitation of 4～5 mm. However，the stability of 2.4 modulus system is relatively good. And the quality of water glass from different manufacturers with the same parameters is quite different，and the early precipitation of 2.4HP-50 sample is relatively slow. The content of iron ions in samples 1—7 ranged from 0.006 5% to 0.035 0%，iron ion content is not the main factor affecting the stratification of the system，and the highest iron ion content is 0.035% in No.6 sample. However，there is no positive correlation between the content of iron ions and the amount of precipitation，the infrared spectrum of the precipitates of No. 3—6 samples is basically the same，and the main analysis is glycerin and catalyst. It can be determined that the components of the precipitates are the same. Therefore，the main reason for the precipitation of the system is that the amine catalyst breaks the charge balance of the water glass colloid. According to the similar phase solubility theory，the alcohol amine catalyst brings the glycerine out of the system together to cause the white material stratification.