In reality the charge on the dust grain varies both with space and time due to the electron and ion current flowing into or out of the dust grain, as well as other processes like secondary emission,photoemission of the electrons and etc.The dust charge fluctuation would be important for studying the behavior of dusty plasmas.Today the study to non-linear wave in inhomogeneous dusty plasmas is focused on one-dimensional and it is very small to three-dimensional.A modified variable coefficients Korteweg-de Vries (MKdV) equation is derived by using the reductive perturbation method with the inhomogeneity, the dust charge fluctuation,the dust temperature, and the external magnetic field.The results show the inhomogeneity, the dust charge fluctuation,the dust temperature,and the external magnetic field influence the propogation of three-dimensional nonlinear waves. The approximate analytical solution is obtained by using approprate transform.