To measure the scale of agricultural water transfer (AWT) from the perspective of food security, this paper establishes an integrated framework for quantifying its actual scale, theoretical transferable scale, and deviation. Based on panel data from 2001 to 2023 of five cities (Anyang, Hebi, Xinxiang, Jiaozuo, Puyang) of the Wei River Basin in Henan Province, China, the actual transfer scale is derived by comparing agricultural water right allocations with net crop irrigation requirements calculated via the FAO 56 Penman Monteith formula; the theoretical transferable scale is estimated using a translog production function grounded in factor substitution theory. By contrasting the two scales, deviations and excessive transfer scenarios are identified. The results show that (1) actual AWT occurred in 59.13% of the city-year observations, exhibiting clear phase-based fluctuations, with positive transfer scale ranging from 0.046 to 13.983 & times; 108 m3. The largest positive transfer occurred in Puyang in 2002, and Puyang, Jiaozuo, and Xinxiang were the main outflow areas. Factor combinations could release transferable water in 45.22% of the city-year observations, wherein pesticide/fertilizer, agricultural machinery, and grain sown area serve as the main substitutes. Theoretical transferable scale ranged from -60.150 to 186.374 & times; 108 m3, with a mean of 1.718 & times; 108 m3 and a median of -0.108 & times; 108 m3, indicating unstable factor-substitution capacity. (2) Excessive transfer was identified when the actual transfer scale was positive and exceeded the theoretical transferable scale. Under this criterion, 47.82% of observations were excessive transfers, 11.33% were reasonable transfers, and 40.85% showed no transfer. Jiaozuo and Puyang were the core excessive transfer areas, each showing excessive transfer in 16 of the 23 years, while Xinxiang has shown a rising trend in recent years; Anyang, by contrast, effectively controls excesses through water saving technologies. The findings highlight the need for dynamic monitoring, city-specific regulation, and advanced water-saving technologies to balance water allocation with food security.