Two field experiments were conducted at the Experimental Farm of the Rice Research and Training Center (RRTC), Sakha Research Station, Kafrelsheikh, Egypt, during two seasons of 2016 and 2017 to study the response of some rice cultivars to some potassium rates. The experimental design was a split- plot system with three replicates. The main plots were occupied by the eight rice cultivars “Sakha 101, Sakha102, Sakha105, Sakha106, Giza 177, Giza178, Giza179 and Giza 182". While, the sub-plots contain four Potassium rates (0, 50, 100and 150% from recommended of K=RDK). Panicle length (cm), number of filled grains/panicle, 1000- grains weight (g), biological, grain, and straw yields (t/ha.), hulling %, milling %, GT%, amylose, grain K content, grain protein content (%) were determined in both seasons. The obtained results revealed that all cultivars were affected significantly regard their respect to K fertilization due to their genetically differed. Moreover, the rice cultivars Giza 178, Sakha 101 and 102 had a significant response with increasing K- fertilizer rate up to 150 from the recommended dose (RDK) as compared with other cultivars under the study