The printed circuit heat exchanger (PCHE) has emerged as the preferred recuperator for the primary circuit heat exchanger in molten salt reactors (MSRs) due to its superior heat transfer efficiency, compactness, and excellent resistance to pressure and temperature. However, the narrow flow channels of PCHEs are susceptible to blockages caused by impurities, which can lead to localized overheating, increased pressure drop, and potential system destabilization. This study investigates the effects of flow blockage on the thermal-hydraulic performance of a zigzag PCHE using three-dimensional numerical simulations with ANSYS FLUENT software. The study analyzes the changes in thermal-hydraulic characteristics of fluoride salt within the zigzag PCHE under scenarios with blockage ratios ranging from 0 to 75%. The results indicate that the heat transfer power decreases significantly with increasing blockage ratio due to the reduction in effective heat transfer area. Additionally, both global velocity and temperature decrease along the flow direction as the blockage ratio increases. This study provides critical insights into flow blockage accidents in zigzag channel PCHEs, offering valuable guidance for enhancing the safety and reliability of such systems.