This talk is concerning a chaotic oscillation of a nonlinear model of turbine rotor. Melnikov’s method is one of the most important methods in determining chaos, but the practical model prevents the application of Melnikov’s method because its complicated nonlinearity makes difficulties to count the number of equilibria, not mentioning the determination of stability and the computation of heteroclinic orbits. In this work, a numerical algorithm is given to compute Melnikov functions with an idea of avoiding the computation of . heteroclinic orbits. The convergence of the algorithm and the estimates of errors help us to give a parameter region for chaotic oscillation of the rotor.