The invention discloses a supercritical water cooled reactor based on stacked fuel assemblies. The supercritical water cooled reactor based on stacked fuel assemblies comprises fuel assembly channelsand control rod assembly channels; the fuel assembly channels and the control rod assembly channels are both regular hexagonal or square; fuel assembly channels are continuously distributed on the outer side of each control rod assembly channel along the circumferential direction to form a unit assembly, and a plurality of unit assemblies are distributed in a staggered array to form a honeycomb-shaped reactor core integral structure; fuel assemblies with different enrichment degree standards are arranged in the fuel assembly channels, and the enrichment degree of the fuel assemblies is gradually increased in the axial direction of the fuel assembly channels from bottom to top; and control rod bundles are installed in the control rod assembly channels. According to the supercritical water cooled reactor based on stacked fuel assemblies, without introducing moderated water rods and a multi-flow flow scheme, the key problems of overlarge axial temperature and coolant density change, unbalanced neutron moderation capability distribution of the reactor cores and the like of the supercritical water cooled reactors are effectively solved, the fuel assembly and reactor core arrangement scheme is remarkably simplified, and the engineering realizability is improved.