SUN Hung Kai Properties has entered into an $800 million property joint venture in Shanghai. A company representative said Shanghai, China's largest city, provided a desirable environment for investors. She said Sun Hung Kai held a controlling stake in the project, which is a joint venture with Shanghai Fuxing Development Corp and ''a number of multi-national enterprises''. The partners signed an agreement last Friday with the Shanghai municipal's Luwan district authorities to undertake the project. The project will involve the development of an 8,000 sq metre site at Huai Hai Middle Road, one of the busiest streets in Shanghai. It will provide 48,000 sq metres of office and shopping space on completion in 1996. Sun Hung Kai is adopting a prudent policy in pursuing investments in China. Its mainland investment will not exceed 10 per cent of the group's total business. Its policy is to focus on selective investment projects in Beijing, Shanghai and Guangzhou. In Beijing, Sun Hung Kai is engaged in a joint venture with the DongAn Group to redevelop the DongAn market in Wangfujing into a 1.8 million sq ft commercial complex. In Guangzhou, it is involved in a joint venture to redevelop Nan Fang Building.