Abstract: Evaporative cooling, achieved through the combination of spray and fan, is one of the most common and efficient methods for cooling cows. Previous studies have shown that spray-fan system reduced respiration rate, body temperature, and culling rate, while increasing milk productivity. However, the use of the spray-fan cooling system can be costly in terms of water and electricity, and it generates a large amount of wastewater. An ideal cooling system should enhance cows’ thermal comfort while minimizing resource costs. Numerical simulations have proven that changing the spray direction from perpendicular to parallel relative to the cow’s body could reduce water consumption while potentially improving the cooling effect. Additionally, spray frequency is another key factor influencing the balance between cooling effectiveness and water efficiency. For now, a proper evaluation of how different spray directions and frequencies impact the cows’ physiological responses, if any, has not been conducted, nor has there been an assessment of the optimal strategy to balance the cooling effect and water efficiency. Consequently, the objectives of this study were to 1) evaluate the cow’s physiological responses (rectal temperature and respiration rate) to the different spray directions and frequencies; and 2) determine the optimal spray strategy that balances the water efficiency and cooling effectiveness. A total of 20 Holstein cows were randomly assigned to five treatments with a cross-over design: no spray; spray perpendicularly for 40 s on and 300 s off (8 cycles); spray parallelly for 40 s on and 300 s off (8 cycles); spray parallelly for 20 s on and 320 s off (8 cycles); spray parallelly for 40 s on and 640 s off (4 cycles). During the test period, each group of cows was tested either between 11:00 and 12:30 or between 14:00 and 15:30, with each cow undergoing testing at the same time throughout the trial. All five treatments were tested daily across both groups, and each treatment was replicated three times per cow over a total of 15 days. The order in which treatment was received by each cow was balanced and randomized. Results showed that baseline rectal temperature and respiration rate affected the magnitude of the changes, with cows exhibiting a greater reduction when their initial respiration rate and rectal temperature values were higher. The parallel spray direction with a spray frequency of 40 s on and 300 s off resulted in the greatest reductions in rectal temperature (0.55 to 0.62℃ lower than the baseline value) and respiration rate (12 to 20 breaths/min lower than the baseline value). Under the specific environmental conditions of this study, spraying cows in a parallel direction and shortening the spray-on duration from 40 s to 20 s (spray-off duration was 320 s) resulted in similar reductions in rectal temperature and respiration rate as parallel spray direction with a 40 s spray-on duration (spray-off duration was 300 s), over most of the measurement period. In addition, spraying cows with a shorter spray-on duration could consume less spray water (50 percentage points lower). In conclusion, spraying cows in parallel may be a more effective method, especially as smart and precision cooling spray systems gain popularity. In practice, the optimal spray strategy should be determined by comprehensively balancing cooling effect and water efficiency, taking into account specific on-site conditions.