The invention discloses an ecological building block, which comprises a basic block monomer, the middle of which is opened with a plant growing cavity; the front wall of the plant growing cavity is an exterior surface, the back wall thereof is an earth-retaining surface, and two side walls thereof are transversely provided with ecological holes; and the width of the exterior surface is less than that of the earth-retaining surface. The ecological building block has simple structure and low cost, can reduce construction cost by 10 to 20 %, is simple and convenient to construct, reduces land occupation furthest, and increases land utilization value. A garden retaining wall or river channel revetment made from the ecological building block is not only beneficial to growing of animals and plants, causes the wall or the revetment full of vitality and aesthetic perception, but also beneficial to ecological environment protection.