The invention discloses a semi-interpenetrating-network nano composite hydrogel with biocompatibility and temperature sensitivity, and a preparation method and application thereof. The preparation method comprises the following steps: dispersing Laponite in water, evenly stirring to obtain a transparent dispersion, sequentially adding biocompatible alginic acid or alginate and N-isopropylacrylamide monomer, evenly stirring, deoxidizing, adding an initiator, filling the reaction liquid into a reaction die, sealing, and carrying out in-situ free radical polymerization reaction at 15-25 DEG C to obtain the target product. In the prepared hydrogel, the NC (nano composite) gel crosslinked network provides the temperature sensitivity, high strength and high toughness, and the semi-interpenetrating alginic acid or alginate enhances the biocompatibility; and therefore, the temperature-sensitive semi-interpenetrating-network hydrogel has the advantages of high strength and high toughness in the nano composite hydrogel as well as favorable biocompatibility. Cells can adhere to the surface of the hydrogel and proliferate to form a cell sheet, thereby lowering the ambient temperature of the gel and implementing quick desorption of the cell sheet.