Abstract: Trifluralin-loaded microcapsules were prepared by in situ polymerization using chitosan and methyl methacrylate as carrier materials in order to enhance its photo-stability and effective utilization. The surface morphology, size and size distribution, encapsulation efficiency and loading content of the resulting microcapsules were determined. The release characteristics and the photo-stability in soil and water of the microcapsules were studied. The trifluralin-loaded microcapsules dispersed as individual particles with a well-defined spherical shape with average size 6.5 μm. Most of the microcapsules were between 3 and 10 μm. The encapsulation efficiency and loading content of the microcapsules were 79% and 45%, respectively. The trifluralin-loaded microcapsules had a good sustained release performance and the release was controlled mainly by Fick diffusion. Compared with trifluralin emulsifiable concentrate, photo-stability of the microcapsules was enhanced with the half-lives 22 d in soil and 173 min in water under the experimental conditions.