Citing a report prepared for the Defense Department by the Defense Science Board, the newspaper said the compromised designs included combat aircraft and ships, as well as missile defense systems vital for Europe, Asia and the Gulf.
Among the weapons listed in the report were the advanced Patriot missile system, the Navy's Aegis ballistic missile defense systems, the F/A-18 fighter jet, the V-22 Osprey, the Black Hawk helicopter and the F-35 Joint Strike Fighter.
The report did not specify the extent or time of the cyber-thefts and did not indicate if they involved computer networks of the US government, contractors or subcontractors.
The Post said the computer espionage would give China knowledge that could be exploited in a conflict, such as knocking out communications and corrupting data. It also could speed Beijing's development of military technology and boost the Chinese defense industry.
In a report to Congress earlier this month, the Pentagon said China was using espionage to modernize its military and that its hacking was a serious concern. It said the US government had been the target of hacking that appeared to be "attributable directory to the Chinese government and military." China dismissed the report as groundless.