In the seafood industry, a large amount of salt is added to preserve seafood products. During processing, it is necessary to desalt the products for the sake of customers’ health. Unlike a large-scale factory, many small enterprises lack tools and methods for desalting and measuring the efficiency of the desalting process. We have developed a rapid prototype salt-sensing system that can measure the desalting efficiency. Dried salted jellyfish are used as testing materials to evaluate the system. The rapid prototype comprises a microcontroller, a wire, and a liquid crystal display. Using a simple mapping between electrical conductivity and actual data obtained from the measurement of samples, the sensing system is successfully calibrated. A method of desalting the salted jellyfish material is also proposed. This desalting method and the newly developed simple sensing system for the desalting process are expected to make a significant contribution to the seafood processing industry.