The invention discloses a safety analysis calculating device for transient nuclear heat coupling of a supercritical water reactor, and belongs to the field of nuclear power plant design and reactor safety analysis. The safety analysis calculating device for transient nuclear heat coupling of the supercritical water reactor is applicable to the supercritical water reactor. According to the safety analysis calculating device, a transient physical analysis program is built by using the space-time disperse solution of a double-group space-time kinetic equation, a transient heat engineering analysis program is built through calculation of flow distribution among channels and the solution of flowing heat exchange inside the channels, on this basis, a physical calculation program is embedded into a transient system analysis program to build a supercritical transient coupling analysis program so as to analyze safety of a system. Particularly, due to the fact that a space-time kinetics quasi-static solution model built through the double-group neutron space-time kinetic equation is combined with a multi-channel analysis method, compared with a sub-channel model, the calculation time is shortened on the basis that precision is ensured, then economy of the supercritical water reactor design is improved, and the safety analysis calculating device accords with the development trend of safety analysis.