the carrageenan from Kappaphycus alvarezii were extracted using hot water or hot alkali which was developed using ultrasonic waves. The purpose of this study was to determine the quality and quantity of the results of extraction by ultrasonic wave method using Elma sonicator. Whereas for the variation of the use of the Elma sonicator tool, the extraction time variations were 20, 30, 40, 50 minutes and temperature variations of 50, 60, 70, 80˚C for a maximum of 50 minutes. Carrageenan quality tests carried out include water content, viscosity, and gel strength. The results of this study showed the highest yield of carrageenan with a variation of extraction time of 50 minutes at a temperature of 80˚C, ie 54.0671%, water content 2.5-9%, viscosity was 5-40 cP, and the strength of the gel was 300- 16000 dyne / cm2.