Thermoplastic polyurethane, composed of soft domain and hard domain because of microphase separation, has caught extensive attention in academic and industrial fields due to its characters of excellent of wear and tear resistance, flexibility and recyclable. Hydrogen bond, resisting in the soft domain and hard domain, has endowed TPU with the structure of physical crosslinking. Due to these characters, the TPU foamed material has serious cell shrinkage behavior at room temperature. This shrinkage behavior makes the application of thermoplastic polyurethane foaming material more uncertain and more difficult. In our study, the cell shrinkage behavior of several kind of TPU was investigated in detail. The result showed that the microcell shrinkage behavior of the scCO2 foaming TPU material was closely related to the viscoelasticity of the TPU molecular chain and microphase separation structure. As for TPU foam with the low Glass transition temperature and low crystallinity, the CO2 dissolved in the soft domain of TPU is easy to follow out at the room temperature in short time (~24 h). Interestingly, the molecular chain of TPU is easy to rebound after being stretched through the simulating foam process, resulting in the microcell shrinkage of TPU foam. The microcell shrinkage mechanism of scCO2 foaming TPU material was also proposed.