The trial opened at 8 a.m.
Prosecutors accused Tian Wenhua, Sanlu's former board chairwoman and general manager, and three other executives of producing and selling fake or sub-standard products.
Sanlu Group Co., Ltd., represented by its trade union chairman Ran Weiguang, was also a defendant.
The three other executives are former deputy general managers Wang Yuliang and Hang Zhiqi, and Wu Jusheng, a former executive in charge of the milk procurement division.
All four defendants were arrested on Sept. 26.
At the end of the trial, Ran, on behalf of Sanlu, offered apologies to children sickened by the tainted milk and their families.
The verdict will be announced at an unspecified future date.