In order to solve technical problems of cost and system complexity because that the control principle based on a CPU configuration in the prior art is directly used in a variable forcing and releasing technical scheme employing an FPGA controller, the invention provides a variable forcing and releasing device and method for an instrument control system of a nuclear power station, wherein the device and method can quickly complete variable forcing /releasing, and does not increases the hardware cost. The device comprises a variable forcing module, a variable releasing module, a forcing variable storage region, an MNET protocol module, and a logic operation module. The device also comprises a multi-path selection module which is located between the logic operation module and the forcing variable storage region. The multi-path selection module is used for enabling at least one forcing and/or releasing variable in the forcing variable storage module to be transmitted to the logic operation module in a parallel signal mode.