Can i marry a u.s citizen using my 30days grace period?

Someone who marries a US citizen is considered an immediate relative under US immigration law, and such individuals are allowed to adjust status even if they have overstayed their visas. In your case, the 30 day grace period is recognized as a period of legal stay. But even if you exceeded it before filing for adjustment of status, you would still be eligible for permanent residence. Due to the limitations of the Lawyers.com Forums, Alan Lee, Esq.'s (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.