The current research was conducted to investigate the knowledge impact of farmers' extension program in the field of using and rationalizing irrigation water, to achieve the research objectives, Ras Sidr and Al Tore cities destrects, South Sinai Governorate were selected as a geographic field for the study sample, a randomized sample of 91 farmers representing (8.3%) of the farmers totaled 1102 at the study area, - Results showed that most of the respondents (74.7%) fell under the medium category of indicator of farmers' knowledge level to the optimum recommendations on using and rationalizing irrigation water before exposing to the extension program, indicating an average level of respondents' knowledge to the optimal recommendations before exposing to the extension program. Results indicated a knowledge gap for respondent farmers in terms of using and rationalizing irrigation water with (55.7%) of the total knowledge to the technical recommendations. It was also indicated that most of the respondents (93.4%) came under the high category of the indicator of farmers' level of knowledge to the optimum recommendations after exposing to the extension program, indicating a positive educational impact of the studied extension program on the trainees' respondents regarding using and rationalizing irrigation water at the study area. Results also showed six variables out of the total independent variables which explain around (36.4%) of the total variation of respondent farmers' level of knowledge to the optimal technical recommendations on using and rationalizing irrigation water at the study area after exposing to the studied extension program ( the subordinate variable) using the Step Wise regression i.e. readiness to change, source of irrigation water, size of animal holding, duration of the training program, attitude toward agricultural extension and non-official social participation.