In this study, we propose a scheme to transform quantum entangled states. In this scheme, a quantum controlled-not (CNOT) gate is realized in coupling systems of the nitrogen-vacancy (NV) color center in diamond and microtoroidal resonators (MTR). A quantum entangled W-state is converted to an entangled GHZ-state based on the cross-Kerr nonlinearity. The scheme displays a high conversion efficiency under the current experimental conditions. This may effectively assist in the preparation of quantum entangled states and the implementation of quantum information processing.