This is the most significant drop in the company's quotations for the last 9 months.
The sale began after the company announced that it had postponed the launch of its mobile game Diablo Immortal in China, which was previously scheduled for June 23.
NetEase developed the game in conjunction with Activision Blizzard.
The companies hoped that China will be the largest market for Diablo Immortal. No new release date has been announced at this time.