A pneumatic tire for all-terrain vehicle is disclosed which comprise a tread, and a plurality of primary blocks extending in a tire circumferential direction disposed symmetrically on the tread with respect to a center line of the tread, each primary block being evenly spaced with each other; two pairs of secondary block arrays arranged respectively on areas between any two adjacent primary blocks which are symmetrical with respect to the circumferential center line of the tread; a prior ground engaging edge created on a ground engaging surface when the ground engaging surface of the primary blocks may be inclined to a moving direction of the tire; and a plurality of stepped humps located on the prior ground engaging edge. The turning manipulation performance of the tires in sandy land can be highly improved while the straight-running traction performance is not affected due to the above configuration of the invention.