How to delete spam messages received on Apple's mobile phone calendar?

Open iCloud and close the calendar item. Then open the mail-address book-calendar option, and close the last item "What was found in the mail".

First go to "Calendar-Inbox" and select "Reject" on the invitation email.

Next, in order to prevent criminals from stuffing advertisements into our calendar, we need to open the webpage version of iCloud, log in to the calendar, and click the preferences in the lower left corner.

Set according to the figure below.

Click Save after setting, and all calendar invitations will be sent to the mailbox first. We can choose whether to join the calendar or not.

Of course, this is only a temporary solution, not a permanent cure. As long as Apple doesn't plug this loophole in the system, those criminals will still find other ways to keep harassing everyone.