Supposing the nonlinear term bounded,by using homotopy invariance theorem,we proved the existence of solutions of boundary value problems for a class of nonlinear ordinary differential equations.When the value of nonlinear term is naught,the conditions of boundary value will guarantee an unique zero solution existing for the corresponding problem.There for the conditions of boundary value may be special,but the forms vary.Furthermore,the method is also available to some high-order boundary value problems.