The invention relates to an HA (hydroxyapatite) nanometer fiber-reinforced silicon-based composite resin for restoration of dental department and a preparation method thereof. The HA nanometer fiber-reinforced silicon-based composite resin is prepared from a resin substrate and an inorganic filler. The preparation method comprises the following steps of (1) preparing an HA nanorod by an equal-phase precipitating method; (2) using polyvinylpyrrolidone as a template agent, and spinning in an electrostatic way, so as to prepare an HA nanometer fiber; (3) using gamma-methylacryloyl propyl trimethoxy silane as a modifier to modify SiO2 (silicon dioxide); (4) uniformly mixing the resin substrate, the SiO2 powder and the HA nanometer fiber according to a ratio, and photocuring, so as to obtain the composite resin. The HA nanometer fiber-reinforced silicon-based composite resin has the advantages that the structure of the HA nanometer fiber is similar to the structure of HA nanobeam in tooth enamel, and the HA nanometer fiber is uniformly dispersed in the silicon substrate, so that the physical and mechanical properties of the composite resin are greatly improved; the bending strength, bending modulus and compression strength are higher; the technology is simple, the preparation conditions are mild, the HA nanometer fiber-reinforced silicon-based composite resin is suitable for large-batch production, and the application prospect is good.