An inlet guide vane assembly is disclosed, which comprises: a housing, configured with a first penetration part and a plurality of first grooves; at least one fixing ring, each configured with a second penetration part and a plurality of second grooves; at least one rotary ring, each configured with a third penetration part and a plurality of sliding chutes, wherein the first, the second and the third penetration parts are arranged in communication with one another; a plurality of vane units, each vane unit is composed of a vane, a linkage and a sliding block; and at least one driving unit, for driving one vane of the plural vanes to swing, thus driving the rotary ring to rotate simultaneously, bringing along the other vanes to swing, enabling the sliding blocks to slide inside corresponding sliding chutes, and consequently flipping the vane from a first state to a second state.