The reaction mechanism between Zn2+ and diatomite in preparation of Zn2+/diatomite antibacterial agent by diatomite adsorbing and solidifying Zn2+ in its pores was studied. Microporous adsorption, characterized by hydrated Zn2+ adsorbed in the micropores of diatomite, and surface coordinate adsorption, featured with coordination of Zn2+ with functional groups on the surfaces of diatomite, were the main adsorption ways accompanied by ion exchange adsorption and physical adsorption. SEM was used to observe the morphologies of diatomite before and after adsorption. Due to the dehydration between OH groups on the surfaces of diatomite when heat treated at high temperature, Si-O-Zn bonds were formed, combining Zn2+ with diatomite together. Reaction model between Zn2+ and diatomite was established.