We study the chemical potential effects on the chiral phase transition in a simply improved soft-wall AdS/QCD model, which can realize consistently the properties of linear confinement and spontaneous chiral symmetry breaking. The $��-T$ phase diagrams with both zero and physical quark masses have been obtained from this model. For the case of physical quark mass, the chiral transition has a crossover behavior at low chemical potential. With the increase of the chemical potential $��$, the critical temperature $T_c$ descends towards zero, and the crossover transition turns into a first-order one at some intermediate value of $��$, which implies that a critical end point naturally exists in this improved soft-wall model. All these features agree with our current perspective on the QCD phase diagram.