After some major redesign works, initial improved Type 039A submarine (No.321) joined solution in April 2001, connected with another (No.322) in Dec 2001. .Since then more vessels are entered solution because of the PLA Navy. Elimination from the stepped design for conning tower could be the main creative cue for recognition of 039A variation. A new layer of anechoic tile happens to be placed on further reduce the sound. Weighed against Type 039, the underwater performance and sound degree of sort 039A submarine was in fact more satisfactory.