Ag nanoparticles were employed as catalyst and their effect on the reaction rate of the nitro-compound were investigated. Results show that Ag nanoparticles can greatly accelerate the reduction of nitro-compound at room temperature, and the nitro-compound with positive charges has higher catalytic reaction rate than that with negative charges. More Ag nanoparticles lead to higher reaction rate; however, the amount should be limited due to the properties of the nanoparticles. The bigger the Ag nanoparticle size is, the higher the reaction rate is.