The invention discloses eco-concrete with compressive strength of 120-200 MPa and a preparation method thereof. The eco-concrete consists of the following components in parts by weight: 600-750 parts of eco-cement, 400-450 parts of fly ash microspheres, 1000-1600 parts of sand, 150-160 parts of steel fibers, 8-12 parts of a high-efficiency water reducing agent, 0.1-0.3 part of a defoaming agent and 156-210 parts of water. The eco-cement consists of a powder material and an additive, wherein the powder materials is at least one selected from a group consisting grey rock, limestone, volcano ash, volcano pumice, basalt, illite, montmorillonite, feldspar, shale, kaolin, clay, wollastonite, gangue, silica fume and fly ash, and the additive is at least one selected from a group consisting of halides, carbonates, sulfates, alkaline substances of amine, silicates, aluminates, alkali metal hydroxides and alkaline-earth metal hydroxides. The eco-concrete has low costs, is energy saving and environmentally friendly, has easily achievable raw materials, has good fluidity, and is easy for construction.