The output of nuclear measurement systems has long been susceptible to electromagnetic interference due to the inherently weak nature of their signals. To address this challenge, this paper proposes a novel active noise reduction method specifically tailored for nuclear measurement signals. This method leverages the power supply characteristics of external nuclear instrumentation systems in Pressurized Water Reactor (PWR) nuclear power plants. Experimental results demonstrate that the proposed method achieved an effective noise reduction rate of 78.1%. Furthermore, an active noise reduction model for electromagnetic interference in nuclear signals is established, offering a valuable tool for the analysis and processing of similar issues in the field.