Microsoft "surprised" but will continue offering Windows 7.
China has banned its government from using Windows 8, Microsoft's latest operating system.
China's official Xinhua news agency said that the ban was to ensure IT security following the Windows XP end of support in April 2014.
However, the ban was ushered in by the Central Government Procurement Center under an energy-saving notice.
Microsoft said it was surprised at the move, but insisted the firm would continue to provide older versions of Microsoft software to Chinese authorities.
Xinhua news agency reported: "The Chinese government obviously cannot ignore the risks of running OS without guaranteed technical support.
"It has moved to avoid the awkwardness of being confronted with a similar situation again in future if it continues to purchase computers with foreign OS."
A Microsoft spokesperson said: "Microsoft has been working proactively with the Central Government Procurement Centre and other government agencies through the evaluation process to ensure that our products and services meet all government procurement requirements.
"We have been and will continue to provide Windows 7 to government customers. At the same time we are working on the Window 8 evaluation with relevant government agencies."