The invention discloses a preparation method of 3D printed magnetic resonance developing hydrogel, comprising the following steps: (1) preparation of printing ink: adding a polycaprolactone-gelatin compound, methacrylic acid modified gelatin, a magnetic resonance imaging contrast agent and a photoinitiator into the deionized water, uniformly mixing, preparing the printing ink and storing for use;(2) design and loading of a 3D model: designing a model by the use of 3DS Max software, importing the model into a 3D printer control software, carrying out slice processing and designing the internalprinting structure; (3) 3D printing preparation: transferring the printing ink prepared in Step (1) into an extrusion barrel of the 3D printer, printing to prepare an initial product of the magneticresonance developing hydrogel, and immediately solidifying the initial product of the magnetic resonance developing hydrogel with ultraviolet irradiation so as to obtain a finished product of the magnetic resonance developing hydrogel. By combining the 3D printing technology with the magnetic resonance imaging, the prepared hydrogel has a fine structure inside and can achieve magnetic resonance developing, controllable preparation of the hydrogel structure is realized and functions of the hydrogel are enriched.