Polyhedral Oligosilsesquioxane (POSS)‐terminated linear block biodegradable polyesters with highly tunable degradation rate and crystalline properties were synthesized. The influences of copolymer compositions and terminal functional groups on the crystallinity and biodegradability were systematically studied by X‐ray diffraction (XRD) and differential scanning calorimetry (DSC). Furthermore, by polarizing optical microscope, X‐ray photoelectron spectrometer, XRD, and DSC tests, the degradation processes both in natural environment and phosphate buffer saline were apparently revealed. Precisely, this work revealed that the crystalline behavior and degradation rate of PCL‐b‐PLLA films could be well controlled by copolymer compositions and terminal functional groups, which is conduced to guide the synthesis of degradable polymers with expected degradation properties and to design heat‐multiresponsive shape memory materials.