Based on a comprehensive analysis of the structure composition and operational characteristics of irrigation districts, a safety evaluation indicator system for large-scale irrigation district projects was constructed from five aspects: channel engineering risk, risk of other structures, rainstorm and flood risk, earthquake and frost risk, and operation and management risk. The system includes 20 indicators, such as canal slope landslide, main structure instability, energy dissipation failure, structural seismic damage, and historical hazard events. The order relation analysis method and the coefficient of variation method were employed to calculate the subjective and objective weights of the evaluation indicators, respectively, and combined weighting was determined based on game theory, which effectively improved the accuracy and reliability of the indicator weighting. Furthermore, the Pythagorean fuzzy number was introduced into the traditional cloud model, and a Pythagorean fuzzy cloud model suitable for the safety evaluation of complex irrigation districts was established. Finally, the model was used to evaluate the safety of a large-scale irrigation district in Henan Province. The results show that the comprehensive safety index of the irrigation district is 0.857, classifying it as “safe”. The safety evaluation results derived from the Pythagorean fuzzy cloud model exhibit high stability, providing a novel method for safety evaluation of large-scale irrigation districts.