Hello Siqi Yang,
Thank you for your post in this Q&A forum.
If you do a GET request with eventid;- /users/{id | userPrincipalName}/events/{id}. The results will get you the event response status
https://learn.microsoft.com/en-us/graph/api/event-get?view=graph-rest-1.0&tabs=http.
Let me know if that answers your question.
Thanks