The utility model relates to an air handling unit of a nuclear power plant. The air handling unit comprises a box body. An air inlet is formed in one end of the box body, and an air outlet is formed in the end opposite to the air inlet. Temperature regulation sections are arranged in the box body at intervals and comprise bypass regulation valves arranged at the windward positions and temperature regulation section bodies arranged at the leeward positions, the bypass regulation valves comprise regulation valve sections and bypass valve sections, and the regulation valve sections and the bypass valve sections are mutually interlocked. According to the air handling unit, it is not needed to additionally arrange an air pipe bypass, the structure is simple, the reliability is high, and the power consumption can be lowered.