Shanghai-listed Pang Da climbed 4.1 percent to 35.39 yuan ($5.44) by midday, compared with an overall 0.6 percent rise in the benchmark Shanghai Composite Index.
Pang Da had surged as much as 4.97 percent in early trade.
Pang Da said Monday it would buy a 24 percent stake in Saab's Dutch owner Spyker for around 65 million euros ($92 million) and purchase 45 million euros worth of Saab-branded cars.
It made the announcement in a filing with the Shanghai Stock Exchange. Spyker had announced the details of the alliance earlier Monday.
The purchase of Spyker's stake is subject to approval from Dutch government agencies, Pang Da said.
The deal also includes a 50-50 distribution joint venture in China and a manufacturing joint venture for both Saab-branded cars and a new "indigenous" car brand aimed at the Chinese market, the statement said.
Saab will hold up to 50 percent of the manufacturing joint venture, with Pang Da and a yet-to-be-determined manufacturer sharing the remainder, it said.
Vehicle sales in China, the world's largest auto market, rose more than 32 percent last year to a record 18.06 million units on government incentives and strong economic growth.
Pang Da, based in Hebei province in northern China, raised six billion yuan in an initial public offering in April. It sold 470,000 vehicles last year with a net profit of 1.2 billion yuan.