how can i be a permanent resident in united state if im here legally as an exchange student on a j1 visa and my visa soon expire

The first question is whether you are subject to a two-year home residence requirement by virtue of your having taken an exchange visitor visa. If you are, you would not be able to immigrate unless the two-year requirement is completed or waived. If you are not subject, US immigration laws allow immigration generally through family or employment-based petitions, immigrant investment, or political asylum, etc. As a J-1 holder, your opportunities may also depend upon the type of J category to which you belong. If you are a research scholar, you may be able to interest an institution to sponsor you for an employment visa and ultimately permanent residence. If you are extremely good in your field, the process may be quicker. As your question is very short as to your particulars, you may wish to consult an experienced immigration lawyer so that he or she can go over your various options.  

The most common way someone becomes a permanent resident is through a family member who can petition for them, or an employer willing to offer permanent employment and go through the labor certification process for you.