The application of new nano-silver iodide (AgI) catalyst to weather modification was studied. Nano-silver iodide powder with closed ice crystal structure was prepared by using a powder precipitation method at normal temperature and pressure. The size distribution and structural property of the nano-silver iodide were characterized by using field emission transmission electron microscopy and X-ray diffraction spectrum. These characterization results showed that the lattice constant of the nano-silver iodide is closer to the ice than the conventional AgI, the nano-silver iodide has a grain size range of 30-90 nm, higher adsorption capacity and larger specific surface area than the conventional silver iodide.