The invention discloses a fibrous nano silicate concrete admixture. The fibrous nano silicate concrete admixture is a compound prepared by magnesium silicate and calcium silicate in a high molecular polymer dispersing agent water solution, wherein the magnesium silicate is prepared by soluble magnesium salt and soluble silicate according to the mole ratio of 1: 1.2 to 1: 1.6, the calcium silicate is prepared from soluble calcium salt and soluble silicate according to the mole ratio of 1: 1 to 1: 1.5, the soluble calcium salt is magnesium nitrate, the soluble calcium salt is calcium nitrate, the soluble silicate is sodium silicate, a high molecular polymer dispersing agent is shown by a formula shown in the description. The fibrous nano silicate concrete admixture can remarkably improve the early strength of concrete. In addition, the concrete toughness has an obvious improving effect, early hydration of cement can be accelerated, and improvement of bending resistance and tension resistance capability of a cement-based material is promoted.