A three-dimensional ecological floating bed and its water-cleaning method, which is the water cleaning technology in environmental engineering; the said three-dimensional ecological floating bed comprises upper, middle and lower three layers, the upper layer is aquatic plant unit(21), the middle of the central hollow pipe in the upper layer is equipped with overflow water inlet pipe(11), the upper of the hollow pipe is equipped with air inlet pore(2), the top is equipped with drop-down map(9), the lower of the hollow pipe is equipped with water inlet pore(10), shampoo spray is installed in the upper part of the drop-down cap; the middle layer is aquatic animal unit(22), aquatic animal cage(14) is equipped in this layer, perforated board(19) and intermediate water intake loop are equipped in the lower part, sampling pipe(6) is connected with intermediate water intake loop(20); the lower layer is the artificial dielectric unit(23), the artificial dielectric(13) is suspended in the suspending support(12), a bottom support(17) and a bottom water intake loop(18) are equipped in the bottom; a floating bottle(3) is equipped in the peripheral of the ecological floating bed.