In this paper, the existence theorem of two positive solutions is established for nonlinear m-point boundary value problem by using an inequality for the following third-order differential equations $$({phi}(u^{primeprime}))^{prime}+a(t)f(t,u(t))=0,;t{in}(0,1)$$, $${phi}(u^{primeprime}(0))=sum^{m-2}_{i=1}a_i{phi}(u^{primeprime}({xi}_i)),;u^{prime}(1)=0,;u(0)=sum^{m-2}_{i=1}b_iu({xi}_i)$$, where ${phi}:R{ ightarrow}R$ is an increasing homeomorphism and homomorphism and $phi(0)=0$. The nonlinear term f may change sign, as an application, an example to demonstrate our results is given.