Desalination is the process of removing salt content from the air so that it can obtain air that can be consumed by humans, animals, and plants. The membrane is a thin sheet that functions as a filter barrier between the two liquid phases, gas and vapor. This study aims to determine how the performance of the membrane from the carrageenan method in well water desalination using reverse osmosis. The decrease in salt content in the air wells was tested using a refractometer. Well, water treatment uses the reverse osmosis method with variations in well water treatment time of 20, 40, 60, 80, and 100 minutes. Well, water that has been processed is tested for its quality with several parameters, namely, pH, TSS, TDS, COD, odor, taste, and color. The results of the well water treatment obtained a decrease in salt content from 1.3326 to 1.3313. The pH obtained before and after processing was 7.24 and 7.63. Decreased COD levels from 121 mg/L to 8 mg/L. The TSS value was lowered from 133 mg/L to 23 mg/L. The TDS test obtained the same value, namely 1 ppm. For color and odor parameters, well water after processing and before processing has no color and odor. In the water wells before processing and after processing for 20, 40, and 60 minutes the water wells still have a salty taste, while at the processing times of 80 and 100 minutes they do not have a salty taste. The above results show that in conclusion carrageenan membranes can reduce salt levels by desalination using the reverse osmosis method.