The bounded traveling wave solutions of MKdV-Burgers equation with negative dispersion coefficient were studied with resorting to the theory of planar dynamical systems,undetermined coefficients method and homogenization principle.The global phase portraits under different parameter conditions as well as the existent number and existense conditions were obtained for the dynamical system corresponding to the traveling wave solutions of the MKdV-Burgers equation.The relation between the profiles of bounded traveling wave solutions and dissipation coefficient was investigated,and a critical value,different from the one proposed by Bikbaev in his article was provided,which characterizes the scale of dissipation effect is presented.The bell and kink profile solitary wave solutions are presented for the MKdV-Burgers equation.Moreover,approximate damped oscillatory solutions of the MKdV-Burgers equation are obtained according to the evolution relation of orbits corresponding to the approximate damped oscillatory solutions in the global phase portraits.This paper also presents the error estimates between exact and approximate solutions for the approximate damped oscillatory solutions.The error is infinitesimal decreasing in exponential form.Finally,the stability at connective points was proved for the approximate damped oscillatory solutions.