Abstract: In this paper, by the technique and the method of deagonalization, the boundary value problem for second order singularly perturbed nonlinear system as follows is dealt with:εy"=f(t,y,y’,ε),y(0,ε)=a(ε),y(1,ε)=b(ε) The existance of the solution and its asymptotic properties are discussed when the eigenvaslues of Jacobi matrix fy’ has K negative real parts and N-K positve real parts.