China’s big game companies continue to be interested in U.S. game startups.

As part of its first quarter 2010 earnings report, Chinese online game publisher and developer Perfect World Entertainment announced today that it has acquired a majority stake in development startup Runic Games. The company invested $8.4 million in Runic, cementing a relationship that began when Perfect World published Runic’s first title, the Diablo-style dungeon crawler Torchlight. That game has gone on to sell 500,000 units within the first six months.

“As a part of our growth strategy, we continuously monitor the market for acquisition opportunities that will generate synergies with our core business,” said Perfect World CEO Michael Chi. See Industry Gamers for more. And check out our profile of Runic Games from October.