The regulation (in Chinese) http://www.mcprc.gov.cn/whzx/bnsjdt/...05_464422.html
Translation regarding loot boxes:
The regulation will be effective on May 1st, 2017.
2.6 ...Online game publishers shall promptly publicly announce information about the name, property, content, quantity, and draw/forge probability of all virtual items and services that can be drawn/forge on the official website or a dedicated draw probability webpage of the game. The information on draw probability shall be true and effective.
2.7 Online game publishers shall publicly announce the random draw results by customers on notable places of official website or in game, and keep record for government inquiry. The record must be kept for more than 90 days. When publishing the random draw results, some measures should be taken place to protect user privacy.