Multi-responsive block copolymer poly(dimethylamino-2-ethyl methacrylate)-block-poly(lactide) (PDMAEMA-b-PLA) was synthesized by Ring-opening Polymerization (ROP) and Reversible Addition-Fragmentation Chain Transfer Polymerization (RAFT). Structures of the block copolymers were conformed by 1H-NMR and FTIR. The self-assembly of the block copolymers and their particle sizes and morphologies changed with CO2 and pH responses were investigated by ultraviolet spectrophotometer (UV-Vis), zeta potential and particle size analyzer and SEM. Results showed that the block copolymers have pH sensitivity and CO2 responsibility, and the responsibilities to environment can be recycled at least three times.