The invention discloses a reactor shutdown design method capable of effectively eliminating prolonging of the rod drop time of a reactor of a nuclear power plant. A PLC logic control circuit and a three-phase monitoring relay cascading unit which are mutually independent are arranged in a rod control power supply cabinet. According to the reactor shutdown design method, an independent reactor shutdown power-off control circuit which is used for avoiding single faults is added in the rod control power supply cabinet, and is completely independent from original PLC-relevant logic control circuits; moreover, the independent reactor shutdown power-off control circuit is designed by combining single fault prevention and redundancy control, it is guaranteed that the reactor shutdown channel response time meets requirements under various working conditions, and thus the reliability of system equipment is improved.