Understanding of the ice crystallization process plays a key role in storaging cells. Surface of ice is known to be rather hydrophobic and amphiphilic block copolymers with appropriate hydrophobicity can adsorb on the ice surface to inhibit the growth of ice crystals. Here we synthesized poly(ethylene glycol)-poly(L-alanine) block copolymers with various block length. Depending on the block length of the polymers, size of ice crystals varied, and the shape was also diverse from spherical to rod-like sharp shape. Stem cell recovery improved as the size of ice crystal decreased, however it dropped as the ice crystal shape was rod-like shape. The recovered cell exhibited excellent proliferation and underwent into osteo-, chondro-, and adipogenic differentiation. Contrary to dimethysulfoxide (DMSO), current cryoprotectant, PEG-PA proved to be cytocompatible. The paper suggests that PEG-PA (5000-500) can be an excellent cryoprotectant for stem cells to replace cytotoxic DMSO.