Abstract: Nanopesticide is one of the most important strategies to reduce the use of pesticides and their impacts on the environment. To develop a facile preparation with high efficiency, low cost and prompt nanopesticides from laboratory investigation to agricultural application, nanoparticles based on the self-assembling of chitosan (CS) with sodium methyl ester sulfonate (MES) were obtained under mild conditions and were used as carriers for hexaconazole (HAZ), a typical triazole fungicide. The structure, loading and release properties of the nanoparticle was investigated. The nanoparticle was found to be of excellent carrier towatds HAZ. The encapsulation efficiency was dominated by the concentration of MES and totally increased with the increasing MES concentration. The encapsulation into the nano carriers greatly reduced the release of HAZ and the retarding efficacy was enhanced by the increase in the concentration of MES, CS, and the crosslinking agent sodium tripolyphosphate. The release of HAZ was pH-sensitive and preferred in the acidic medium due to the increased permeability of the chitosan nano-shell layer. Compared to the technical HAZ and commercial HAZ-SC, the nanosuspension presented better antifungal activity against Rhizoctonia solani Kuhn in an indoor bioactivity assay. The half-inhibition effective concentration (EC₅₀) was significantly decreased compared with that of the technical HAZ and commercial HAZ-SC, demonstrating that MES/CS nanoparticle was a good platform for nanopesticides with the potential to apply in the fields.