Abstract: In order to study the effect of calcium carbonate on the properties of the new high water filling materials, experiments and electron microscopy (SEM) scanning methods were used to analyze the performance of filling materials and hydrate ettringite microstructure. The results show that heavy calcium carbonate can significantly reduce the compressive strength of filling materials; the main reason is that heavy calcium carbonate slows the formation of ettringite during hydration of high water filling materials, and changes the distribution of ettringite spatial structure of calcium and increases space between ettringite; with the increase of calcium carbonate, the compressive strength of high water filling materials decreases gradually, flowing lose time and hardening time are prolonging.