Check out this fabulously informative article on Chinese SSBNs. The PLAN is building between four and six Jin-class nuclear ballistic missile subs, which when complete will constitute a deterrent on the same order as that possessed by France or the United Kingdom. According to the author, the Chinese believe that SSBN launched missiles can render a missile defense system useless, at least for the current generation of missile defense technology.
I am curious about what the boats mean for the future of Chinese naval doctrine. Whereas British, French, and US SSBN practice has focused on hiding, Soviet naval doctrine envisioned a layered defense of SSBN home areas. The Soviets believed (correctly) that Western attack submarines could detect their SSBNs, and as such structured air, surface, and subsurface doctrine around the idea of protecting base areas from incursion by US subs and surface vessels. It seems unlikely to me that these Chinese submarines will be able to reliably avoid interception and tracking by US submarines, which makes me wonder whether the PLAN will adopt measures similar to those of the Red Navy in the second half of the Cold War. This is relevant because the Soviet naval buildup was misinterpreted until the late 1970s; it took a long time for the USN to figure out that the expansion of Soviet naval capabilities was, in substantial part, oriented around defense of boomers.