Wal-Mart Stores plans to buy a controlling stake in the fast-growing Chinese online retailer, Yihaodian.

The retail chain has agreed to increase its stake in Yihaodian's holding company to about 51 per cent, Wal-Mart said late on Sunday.

The financial terms of the deal were not disclosed. It still must be approved by Chinese government regulators.

Yihaodian sells more than 180,000 products, including groceries, electronics and apparel. It has expanded rapidly since it was founded in July 2008.

It has 5400 employees and a next-day delivery network across Shanghai, Beijing, Guangzhou, Wuhan and Chengdu.

Wal-Mart eCommerce executive Neil Ashe said the deal improves Wal-Mart's access to Chinese consumers who use smartphones and social media to shop.

Yihaodian co-founder and chairman Gang Yu said Wal-Mart's carefully managed supply chain will make the Chinese firm more efficient.