Abstract: A 20% chlorantraniliprole nano suspension was prepared by optimizing the traditional process. The effects of sanding time, sanding speed and additives ratio on the particle size of 20% chlorantraniliprole nano suspension agent were discussed. The particle size distribution, surface charge, contact angle and retention amount were characterized, and the biological activities of nanopesticides and traditional pesticides were compared through laboratory and field experiments. The results showed that the particle size of the 20% chlorantraniliprole nano suspension was between 150-180 nm, the particle size distribution was narrow, and the surface was negatively charged. The particle size of 20% chlorantraniliprole nano suspension decreased with the increase of sanding time and grinding speed. The biological activity of 20% chlorantraniliprole nano suspension against corn borer was higher than that of 20% chlorantraniliprole commercial suspension. The efficacy of the suspension agent was positively correlated with the maximum retention amount and negatively correlated with the contact angle, and the nano size of the nano suspension agent could enhance the absorption and conduction of the active ingredient on the leaves, thereby enhancing the biocontrol effect of the suspension agent.