Soluble starch–based biodegradable and microporous microspheres (SDM-Ms) were prepared by emulsion chemical cross-linking technique using trisodium trimetaphosphate (TSTP) as the cross-linker. The resultant amorphous SDM-Ms were excellently identified by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The internal rupture and surface-controlled erosion were the predominant degradation mechanisms for SDM-Ms. The obtained SDM-Ms were applied to adsorb coix seed oil (CSO) by immersing method. The adsorption capacity of CSO within SDM-Ms was determined, namely 0.5238 g/g, and the thermal stability was shown higher than that of the free CSO. A burst release appeared in the second hour, followed by controlled release. Diffusion, degradation, and erosion mechanisms might coexist for the full release processes. The soluble starch (Ss) was demonstrated a promising biodegradable polymer for preparing the porous microspheres. Meanwhile, after being adsorbed into the SDM-Ms, the CSO can be powerfully applied in food and pharmaceutical industries.