The invention belongs to the technical field of tunnel shield construction, and provides an anti-cracking and anti-floating fiber-reinforced synchronous grouting slurry for shield construction. The grouting slurry is made by mixing cement, medium coarse sand, a montmorillonite ore powder, water, sodium nitrite, a water reducing agent, and monofilament bundle fiber, wherein a mass ratio of water tothe cement is 1.2:1-1:1; a mass ratio of the cement to the medium coarse sand is 0.3:1-0.6:1; a mass ratio of the montmorillonite ore powder to the cement is 1:1; sodium nitrite is 3%-6% of the cement mass; the water reducing agent is 0.2%-2% of the cement mass; and the fiber blending content is 0.1%-0.5% of the cement mass. The bleeding rate is low, the slurry flow is constrained by the dispersed fiber, the consolidation shrinkage is small, the solidified body has good tensile strength, flexural strength, bending toughness, impermeability, durability and other properties, the floating risk of shield segments is effectively reduced, the occurrence of cracks in the grouting solidified body is reduced, and the construction cost is reduced.