Poly–D,L–Lactides (PDLLA1, PDLLA2 and PDLLA3) with molecular weight of 25 000, 60 000 and 100 000 respectively were used as coating material and, polyvinyl alcohol (PVA–1788) was used as emulsifier to prepare PDLLA–Chlopyrifos microcapsule by emulsion solvent volatilization method. The effects of process conditions were studied. The performance of PDLLA–Chlopyrifos microcapsule was characterized by optical microscope, scanning electron microscope, laser particle size distribution device and high performance liquid chromatograph and the performance of sustained release of three kinds of PDLLA–Chlopyrifos microcapsules was studied by column chromatography. The results showed that process conditions had a significant effect on microcapsule diameter, and microcapsule with regular sphere and small diameter could be obtained when PVA–1788 concentration was 1.25%, volume ratio of continuous phase and organic phase was 4.5 and weight ratio of PDLLA and Chlopyrifos was 2∶1. The molecular weight of PDLLA had little effect on appearance, diameter and distribution of microcapsule. Three PDLLA– Chlopyrifos microcapsules showed significant sustained-release effect. And the accumulated release of PDLLA1, PDLLA2 and PDLLA3 19 d after administering were 88.76%, 76.74% and 65.64%, respectively, among which PDLLA1 with the lowest molecular weight (25 000) had the fastest speed of release.