China's officials Xinhua News Agency said the vessel's nuclear devices, including its turbo electric 90MW engine and pressurized water reactor, have been properly disposed of.
Scientists also decontaminated the warehouse where nuclear items were stored during the past 40 years.
The 320-foot-long submarine will become an exhibit after the military releases it from all service, the Xinhua report said.
The Long March 1 -- one of five Chinese nuclear-powered submarines -- was built in 1970 and commissioned into the Peoples' Liberation Navy in 1974, Xinhua reported. The fifth and final boat of the class was commissioned in 1990.
The 5,000-ton submarine belongs to the Han-class nuclear-powered submarine Changzheng Type 091 and can carry six torpedoes or 36 mines.
The submarines have Snoop Tray I-Band Surface Search radar, GlobalSecurity.com reported. The ships also have Trout Cheek hull-mounted active/passive search and attack DUUX-5 passive ranging and intercept sonar.
But the vessel's armament capabilities had become obsolete because of the weapons' short ranges, Xinhua reported.
The remaining Changzheng vessels are reported deployed with China's Northern Sea Fleet and are based at Qingdao, formerly called Tsingtao.
Another report by GlobalSecurity.com suggests that numbers 1 and 2 had radiation problems that were believed solved after extensive refits in the 1980s.
Since the late 1990s, hull 1 had been inoperational and hull 2 likely remains so, GlobalSecurity.com reported. Some analysts believe that, as of 2000, only two of Han-class submarines remain operational.
Xinhua reported the more Xia-class Type 092 ballistic missile nuclear-powered submarines have started patrolling in China's offshore economic zone waters.
SinoDefense.com reported in 2009 that the 393-foot-long Xia-class subs are a stretched version of the Han-class attack submarines to accommodate the missiles The first vessel was commissioned into active service in 1987.
Like the Type 091, the 6,500-ton Type 092 is powered by a nuclear, turbo-electric arrangement, consisting of one pressurized water reactor rated at 90MW.
Type 092 subs carry 12 single-warhead JuLang 1 submarine-launched ballistic missiles -- NATO reporting name CSS-N-3.
It's rare that Chinese media publish photographs of the country's submarines, the FT reported.
Publishing photographs of the 092 shows that the Chinese military is becoming more confident.
"It is still the first time that the Xia-class has been discussed in such detail in China's state-run media," Taylor Fravel, an expert on Chinese security at the Massachusetts Institute of Technology, told the FT. "As China's military modernization continues to advance, the PLA has become more willing to discuss its capabilities."