The invention discloses a backward centrifugal wind wheel. A three-element twisted blade(3) is adopted, a leading edge(31) is rotated along the axis L1 of the wind wheel is intersected with the meridian plane A to form a curve L2, the distance between each point on the curve L2 and the axis L1 of the wind wheel is gradually reduced from the diameter D0 to the axis L1 of the wind wheel, and then the distance is gradually increased from small to small; and the trailing edge (32) and the projection re-plane formed on the cylindrical surface B is unfolded to form a curve L3, the coordinates of thefive curvature inflection points a, b, c, d and e in the curve L3 are coordinates (xa, ya), (xb, yb), (xc,yc), (xd,yd), (xe,ye) wherein the total length of the projection is y, the total width is x.The flow in the whole flow channel is optimized, the pneumatic performance of the impeller is greatly improved, the pneumatic noise of the impeller is reduced, and the noise quality of the impeller isimproved.