The invention discloses an environment-friendly composite high-voltage electric power cable for a smart power grid and a preparation method thereof. The environment-friendly composite high-voltage electric power cable comprises a cable core, wherein a halogen-free high-fire-retardant glass cord filling layer is arranged at the gaps of the cable core, the cable core is wrapped with a halogen-free high-fire-retardant glass fiber tape wrapping layer and an extruded polyethylene inner sheath, the inner sheath is wrapped with a galvanized steel strip spiral armor layer with a clearance therebetween, and a thermoplastic halogen-free low-smoke high-fire-retardant polyolefin outer sheath is extruded at the outermost layer; and the cable core is formed by a communication optical fiber, three power cables and three temperature measurement sensing cables twisted together. The cable is good in insulating performance and mechanical performance, and stable in power transmission, online monitoring and communication transmission, also has the high-fire-retardant, halogen-free, low-smoke and environment-friendly properties, is reasonable in structure and excellent in comprehensive performance, and has better product performance indexes than international standards and good social and economical benefits.