After some major redesign works, initial improved Type 039A submarine (No.321) entered solution in April 2001, accompanied by the next (No.322) in Dec 2001. .Since then more boats are entered service because of the PLA Navy. Elimination associated with the stepped design for conning tower could be the main visual cue for recognition of 039A variation. A new layer of anechoic tile has been applied to further lessen the noise. Weighed against Type 039, the underwater performance and noise level of kind 039A submarine was more satisfactory.