UO₂ microspheres prepared by using the internal gelation process have attracted wide attention due to their good sphericity. However, the internal gelation process still has difficulties, such as the slightly uneven size of the prepared microspheres, which is not conducive to large-scale application. The microfluidic assisted internal gelation process was employed to prepare monodisperse sol droplets, which were solidified and sintered to obtain monodisperse uranium oxide microspheres. The uranium oxide microspheres have a uniform size distribution, with variation coefficient to be less than or equal to 1% and sphericity of 1.01. The microfluidic assisted internal gelation process is simple strategy to prepare high-quality nuclear fuel microspheres.