In this Thesis , our main goal is calculating form factors semi leptonic decay by light cone QCD sum rules approach. This method has advantages rather than QCD sum rules method, The QCD sum rules has had achievements ,But, it would be some problems in short distance expansions that fail in non-perturbative condensate. Fortunately as a result of connection between QCD sum rules and theory of hard exclusive process LCSR is able to solve this problem. Phenomenologically , LCSR has been widely applied to investigate the semi leptonic decay hadrons.
