The present invention relates to a process of preparing a biocompatible temperature-sensitive nano-carrier, which comprises the steps of (a) preparing a polymer dispersion comprising a water-soluble biocompatible polymer with photo-crosslinkable functional group(s), (b) preparing a polymer-initiator solution by adding an initiator to the polymer dispersion, and (c) preparing the nano-carrier by irradiating light onto the polymer-initiator solution, wherein the average diameter of the nano-carrier changes depending on temperature, and also relates to a temperature-sensitive nano-carrier. Nano-carriers of the present invention are temperature-sensitive, and their average diameter and pore size reversibly change in response to temperature change. In an embodiment of the present invention, nano-carriers can be prepared via a one-pot single-phase synthesis. A process of the present invention overcomes the conventional problems such as the use of organic solvent, complicated preparation steps, a relatively high manufacture cost and a low loading efficiency. Moreover, a process of the present invention can ensure the stability of drugs without necessitating high-speed homogenization or ultrasonification generally carried out in the conventional process.