This paper proposes a new method for detecting both OAM and polarization state for a vector vortex beam using rotational Doppler effect. We show that this new approach measures both the absolute value of the topological charge and its sign. Also, the phase and the visibility of the intensity variance give the polarization parameters of vector beam. We have also experimentally proved the feasibility of our method. This method solves the drawback in existing experimental schemes that they cannot measure the topological charge of a vector beam while giving its polarization parameter and overcomes the degeneracy problem in the spectrum analyzer based on the rotational Doppler effect.