Is it illegal to send false court information? How to report it?

Of course it's illegal. Bring a lawsuit to the people's court or report to the people's procuratorate.

Article 2 10 of the Civil Procedure Law stipulates that the procuratorial organ has the right to investigate and verify. This requires the procuratorial organs to investigate and collect evidence strictly within the framework permitted by law. The applicant applies to the procuratorial organ for investigation of a case that may exist in false litigation, or it has a significant impact on national interests and social interests.

The procuratorial organ shall initiate the investigation procedure of illegal acts according to the application or ex officio.