The principle, of which the ZnSe thin films are co-deposited in the ZnSO4 and Na2SeO3 acidic solution by electrochemistry, is explained by the electrode-solution interface action model. The current density and the duty cycle of the pulse current promote the diffusion of solution and affect the co-deposition of the ZnSe films. The ZnSe thin films are pulse electrodeposited in zinc sulfate, selenite sodium and sodium citrate acidic solution. The sodium citrate, which is one kind of complex agent, simultaneous also one kind of buffer agent and has certain buffer action, would affect the quality of the ZnSe films. Finally, the ZnSe films have been characterized by the scanning electron microscope (SEM) and the energy dispersion analysis of X-ray (EDAX).