Experiments were conducted to in An Giang province in a paddy rice field in 2020 and 2021 to determine ET (evaporation) by pan method. And then, comparing these parameters with the model method. From that, calculating water needs for rice crops. In addition, the study pointed out a treatment that had the highest rice yield but the lowest amount of irrigation water to to make recommendations to farmers. Results showed that ETC (mm.day-1 ) and in Winter-Spring, Summer-Autumn, and Autumn-Winter crops are 4.95, 5.27; 3.48 respectively. Rice yield in most of the treatments were higher than the control treatment (Blank test) in both experiment. In the Winter-Spring crop, the yield and percentage of filled grain were higher than in the other two crops. The results also showed that water need were intaken into the rice field determining the survival of the plants by counting the plant density. The selected treatments for recommendations to the population are respectively: TM4 in experiment 2 for Winter-Spring crop (rice yield about 14 tons/ha, water need of 14,000m3 /ha); TM4 in experiment 1 for the Summer-Autumn crop (rice yield 5.8 tons/ha; water need of 7,312m3 /ha); TM2 in experiment 1 for the Autumm-Winter crop (rice yield of 6.74 tons/ha, water demand is 3,204m3 /ha).