How can we find out the criminal judgment or the nature of the case and know that someone has been convicted in other places, involving many people, such as online fraud,

Generally, it should be found on the website of the court.

Constitution of the people's Republic of China

Article 130

The people's courts hear cases in public, except in special circumstances prescribed by law. The defendant has the right to defend himself.

Article 148 of the Civil Procedure Law: The people's court shall publicly pronounce a judgment on a case that is tried in public or not.

Article 202 of the Criminal Procedure Law 1: All judgments shall be publicly announced.

Paragraph 1 of Article 80 of the Administrative Procedure Law: The people's court shall publicly pronounce judgments on cases tried in public and cases tried in private.