The supercritical phase behavior of the poly(lactic acid)/poly(ethylene glycol)/poly(lactic acid) (PLA-PEG-PLA) + CO2 + dichloromethane (DCM) system and the PLA-PEG-PLA + CO2 + DCM + C2H5OH system was investigated using a supercritical phase monitor. The phase behavior data were measured at temperatures from (313.1 to 338.1) K and pressures up to 35 MPa. The results show that the systems exhibit the characteristics of lower critical solution temperature phase behaviors. The effects of temperature, the mass fraction of DCM (or DCM + C2H5OH), the PEG mass fraction in PLA-PEG-PLA, and the molar ratio of DCM/C2H5OH on cloud-point pressure were discussed in detail.