The invention discloses a vegetation concrete block and a preparation method thereof, and belongs to the field of building materials, the vegetation concrete block comprises the following substances by mass: 40 to 60 parts of dead burned magnesia, 150 to 170 parts of ferronickel slag aggregate, 5 to 20 parts of siliceous and silicon-aluminum admixture, 0.2 to 0.8 part of redispersible latex powder, 1 to 2 parts of water release material, 8 to 10 parts of potassium dihydrogen phosphate, 0.5 to 1 part of superplasticizer, and 5 to 10 parts of mixing water; the preparation method comprises the following steps: preparing a potassium dihydrogen phosphate saturated solution as a spray liquid, proportioning other raw materials, stirring, carrying out vibration molding, carrying out spray treatment, removing the mold, carrying out spray maintenance, inspecting, stacking the finished product and the like. After a cementing material is hardened, the phase is stable, the structure is compact, thecementing material has good carbonization resistance, abrasion resistance and corrosion resistance, the cementing material is endowed with good biocompatibility due to the weakly alkaline characteristic, and the cementing material is endowed with an excellent water quality improvement function together with the phase structure and the porous structure.