Supercritical carbon dioxide (scCO2) has gas-like diffusivity and liquid-like density, which has been widely used as a clean and nontoxic solvent in polymer process instead of organic solvent. Our group successfully produced polylactide (PLA) porous scaffolds without any organic solvent, combining annealing process and porogen leaching. Supercritical carbon dioxide was introduced in annealing treatment and morphology of polylactide/polyvinyl pyrrolidone (PVP) blends was systematically studied. The average pore size of PLA scaffolds is larger than that annealing in atmosphere at the same temperature due to the plasticization of scCO2. This suggested that, compared to atmosphere, coarsening behavior could happen at lower temperature in scCO2, as a result, the degradation of PLA was refrained and the mechanical properties of scaffolds were improved.