I am a second-year college student, I want ask how much possibility I can enroll in UCSB if my major is Actuarial Science with GPA 3.7(so far I have 40 units). If UCSB rejected me, can you tell me any other UC I should apply?
You should try and TAG UCSB which means guaranteed admission. I believe AS is part of TAG:
http://admissions.sa.ucsb.edu/docs/default-source/PDFs/ucsb-tag-fall-2016.pdf?sfvrsn=2
I also got into UCSB for Actuarial Science as a transfer for this past application season, and my GPA when I applied was 3.6. I think you should be fine with a 3.7, provided you complete all the prerequisites. TAG is also a good idea.