The invention relates to an antistatic and high-performance PA66 (polyamide66) composite material and a preparation method thereof. The composite material is composed of the following components in parts by weight: 50-70 parts of PA66; 20-30 parts of a modified nano silicon dioxide graft; 6-10 parts of an antistatic agent; 0.1-0.5 part of an antioxidant; and 0.1-0.3 part of a lubricant. According to the technical scheme, the silane coupling agent and the hydroxyl radicals on the surface of the nano silicon dioxide are subjected to condensation, so that agglomeration of the nano silicon dioxide is prevented, the nano silicon dioxide can be uniformly dispersed in the PA66 matrix, and the mechanical properties of the PA66 composite material are improved. The modified nano silicon dioxide graft is a core-shell type graft which is formed by taking a KH550-g-SiO2 as a core and PS (polystyrene) as a shell body, the graft has better dispersity than that of simple nano silicon dioxide, and the graft has an effect of distributing loads uniformly when the composite material is subjected to external force, so that the mechanical properties of the PA66 composite material are improved.