If you want to do graduate studies at same school did your undergraduate have reapply gradute or will they automatically accept you?

There's no automatic acceptance into graduate programs at the same school you attended for your undergraduate degree. You must reapply to the graduate program, just like any other applicant. While your undergraduate record from that institution will be part of your application, it's not a guarantee of admission. You'll still need to meet all the graduate program's requirements, including submitting a new application, transcripts, letters of recommendation, a statement of purpose, and potentially GRE or other standardized test scores.