According to RIA Novosti, a state-controlled Russian news agency, Russia and China are collaborating on a new submarine design (in Russian). The project is being coordinated by Russia’s Federal Service for Military-Technical Cooperation.
Russia has a proud tradition of submarine building, creating many of the most powerful and largest subs in the world, so it’s not surprising that Russian submarine technology is seen as significantly ahead of China’s. Russia helped China develop its submarine building industry, giving it the plans to the Golf Class ballistic missile submarine and Romeo Class attack submarine during the Cold War. More recently Russia supplied China with Kilo Class diesel-electric attack submarines.