In all of my semesters my gpa is greater than 3 except my 2nd semester in which I scored 1.4 gpa my overall gpa is 3.1 . Am I eligible for a valid 3 years work permit.
Have you read the eligibility requirements for a PGWP assuming that is what you may be referring to given there is not a 3 year work permit based on outside Canada study.
Maybe you should share a bit more information of your status whether in Canada or elsewhere.