Soho China, the Beijing real estate developer controlled by billionaire couple Zhang Xin and Pan Shiyi, said today it will add to its stake in a piece of  Shanghai property in the city’s swank Xintianti development area.

Soho will pay 788 million yuan, or $121 million, to Shanghai-listed Hua Li Family Group for a 31% stake in a commercial and office project currently called FuxingLu Soho, according to a statement at the Hong Kong Stock Exchange.    Hua Li is controlled by businessman Wang Weilin, who ranked at no. 349 on the Forbes China Rich List last year with wealth of $480 million as of October last year.

Soho, whose shares trade in Hong Kong, said last October that it had bought a 48% stake in the project. The additional purchase is conditional on approval at a Hua Li shareholding meeting on March 25.

Zhang Xin ranked no. 393 on the 2011 Forbes Billionaires List published last Thursday with wealth of $2.9 billion.  China has a record 115 members of the new list.

Soho has been making a big splash in Shanghai, with four investments since 2009 in key Shanghai areas: one in Jing’an, one along the Bund, one in the new Hongqiao Transportation Hub district and the latest next to Xintiandi.  The booming city has been a magnet in recent years for luxury good companies aiming to reach newly well-off Chinese customers,  as well as international real estate consultants and managment companies helping to manage properties.