This paper investigates the structure and the property of the portfolio frontier with no short selling, on this basis an interval searching approach for solving portfolio frontier problem with no short selling is put foreword. Portfolio frontier with no short selling together with all of its composing parabolas can be conveniently and rapidly determined. The approach is of important theoretical meaning and practical value for solving portfolio optimization problem with large scale covariance matrix and also useful for putting po rtfolio theory and its associate methods into practical use．