Kingfisher is selling a 70% stake in the business - which has 39 stores and more than 3,000 staff - for £140m.
The company had already announced that it was looking for a strategic partner to develop its B&Q business in China.
The transaction, which is subject to approval by the Chinese Ministry of Commerce, is expected to be completed in the first half of 2015.
As well as B&Q, Kingfisher owns the Screwfix, Brico Depot and Castorama home improvement chains.
It also owns 50% of the Koctas brand in Turkey.
"I am delighted to have found a strong retail partner who will help us to release the financial value of our business in China," said group chief executive Veronique Laury.
"This will enable us to focus our financial resources and management talent on the large and attractive European home improvement market."
Beijing-based Wumei Holdings operates about 650 supermarkets and 10 department stores in China, owning brands such as Wumart, Jingbei Shopping Mall, and Merrymart.
Ms Laury recently took over from Ian Cheshire as chief executive.
Home improvements retailer Kingfisher has agreed to sell a controlling stake in B&Q China to Wumei Holdings.