This study evaluated the effect of times and rates of potassium application on yield and grain quality characters of Giza179 cultivar during 2017 and 2018 seasons using this new variety had high yield but had high broken rice percentage which reduced the quality characters. Three times of potassium application as basle, maximum tillering  and booting stages. Apply three levels of potassium fertilizer (0, 58, 116 kg K /ha) have been applied using a split plot design. The results indicated that non-significant was among the times of potassium application on number of panicles/plant, but different graded levels of K significantly influenced the same character for Giza 179. The applying of K at maximum tillering  resulted the longest panicle, the heaviest panicle, the maximum number of filled grains/panicle, the minimum  sterility %,  the highest grain yield (Kg/m²)  and the highest harvest index % as compared to at booting stage and basle. Applying  of 116 Kg/ ha of potassium showed superiority of  Giza 179  for 1000- grain weight,  number of filled grains/panicle, the minimum  sterility %, grain yield (Kg/m²) and harvest index % with insignificant differences between58 and 116Kg K /ha on almost characters under study. Potassium increasing significantly effect on grains quality. Applying at maximum tillering showed superiority of Giza 179 for milling % and head rice %.Based on quadratic regression model indicating the maximum does of K varied according to the K of time of applications. The highest rate observation of K with maximum tillering stage for all  studied characters.