The invention belongs to the technical field of nuclear power plant control systems, and in particular to an online management method for temporary control changes of a nuclear power plant control system. The method comprises the following steps: 1) acquiring data, converting DCS configuration data into configuration text information, converting DCS function drawing from a CAD format file to a JPG image format; 2) establishing a signal mapping relation and a configuration data module state table; 3) establishing a data sheet of risks associated with instrumentation and control equipment, and determining a risk knowledge rule between the module state of software corresponding to instruments and an equipment state; 4) integrating the data and the drawing by using the signal mapping relation and the configuration data module state table as a relational model; 5) during change initiation, check and approval, prompting workers in respective links of change management the influence of the change on the control system; 6) enabling a user to inspect a field configuration data module state and to import the configuration data module state information inspection result into the system; and 7) designing a conflict detection module.