The invention discloses an impeller of a single-air-inlet bidirectional multi-blade centrifugal fan. The impeller comprises a wheel disc, a lower-layer blade, an upper-layer blade, a first wheel cover, a second wheel cover and a third wheel cover, wherein the lower-layer blade, the upper-layer blade, the first wheel cover, the second wheel cover and the third wheel cover are positioned on the wheel disc; the first wheel cover, the lower-layer blade, the second wheel cover, the upper-layer blade and the third wheel cover are sequentially distributed from top to bottom; various blades in the lower-layer blade are arranged in the circumferential direction; various blades in the upper-layer blade are arranged in the circumferential direction; the upper-layer blade and the lower-layer blade aresymmetrically distributed in the radial direction; an inlet mounting angle beta1 of the upper-layer blade is 70 to 90 degrees, and an outlet mounting angle beta2 of the lower-layer blade is 150 to 180 degrees; the various blades of the upper-layer blade are all of front-bending blades; and the various blades of the lower-layer blade are of back-bending blades. According to the impeller, the air volume of the multi-blade centrifugal fan can be effectively improved, and surface pressure pulsation of the blades and vortex noises of blade channels are reduced.