To flesh out the upcoming OS, Microsoft is inviting a select group of Xiaomi users to download the Windows 10 Technical Preview to their phone, and offer feedback.
It's a surprising tie-up, given that Xiaomi has had huge success in using Android to sell its phones. Last year, it became China's leading smartphone vendor, and the company has ambitions to expand globally.
Whether this means Xiaomi will explore using Microsoft's new OS is unclear. In an email, Xiaomi said the testing of Windows 10 was an "experimental program entirely led by Microsoft." The program will only be confined to "power users" of its flagship phone, the Mi 4.
Microsoft made the announcement Wednesday, at an event in Shenzhen, China, a manufacturing hub where the company is trying to drum up industry support for Windows 10.
The OS, which is designed to work across devices including PCs, phones and tablets, will arrive in 190 countries and 111 languages this summer, Microsoft said, without giving an exact date.
The Microsoft announcements at the event were largely focused on China, and appeared aimed to ensure that local users upgrade to Windows 10 once it launches.
Back in January, Microsoft said that Windows 10 would be a free upgrade for users already running Windows 7, Windows 8.1 and Windows Phone 8.1. in the first year its released.
To help roll out the OS in China, Microsoft has struck partnerships with PC maker Lenovo and domestic Internet firms Tencent and Qihoo 360, which will provide upgrade services.
This could help speed up adoption. But Microsoft has often found itself fighting an uphill battle to weed out software piracy in China. At the same time, many PCs in the country continue to use Windows XP, a much older version of the operating system.
Microsoft also faces challenges from the dominance of Android in the country, driven mainly by the sale of low-priced phones. Xiaomi's MIUI software, is a customized version of the operating system that the company updates weekly from user feedback.
But if Microsoft is able to get Xiaomi to build Windows devices, it would represent a big win for the U.S. software giant. Xiaomi is one of the hottest brands in China, and has often been compared to Apple because of its loyal fan base.
Globally, Windows Phone has struggled to take off in the midst of heated competition with Android and Apple's iOS. The OS had a 2.8 percent market share in last year's fourth quarter, according to research firm IDC.