An optical lens, a light-emitting device and a backlight module are provided. The optical lens is used for adjusting light emitted from a light-emitting unit. The optical lens includes a light-incident surface and a light-emitting surface. The light-incident surface encloses a space for accommodating the light-emitting unit. The light-emitting surface is used for receiving and emitting light entering the optical lens via the light-incident surface. The optical lens has an optical axis, with respect to which the light-incident surface is asymmetric.