Solar ponds with a salinity gradient are defined as a large volume of water that is able to collect and store solar energy in the form of heat by eliminating the concurrent current in the middle layer. These ponds consist of three main layers of Upperupper convective zone (UCZ), Non-convectivenon-convective zone (NCZ), which is a layer with density gradient increase in depth direction and storage layer or Lowerlower convective zone (LCZ). Various studies have been performed to increase thermal efficiency and improve the performance of solar ponds. This is based on increasing the temperature of the storage area, reducing heat losses and system stability. However, due to the low thermal efficiency of solar ponds, more studies are needed to develop new methods. Phase change materials are preferred because of their ability to store more energy at low volumes through phase change. Adding phase change materials can increase energy storage in the solar ponds storage layer (LCZ). High latent heat in phase change materials are able to control the temperature of the pool against sudden changes. Therefore, in a certain temperature range, adding units of phase change materials to the solar pond will have a positive effect on maintaining the temperature and stability of the solar pond. In this proposal, the effect of using phase change materials (paraffin wax) in the storage layer of the salt gradient solar pond, will be discussed analytically and numerically, its effect on efficiency, stability, heat extraction and heat loss from the floor and walls of solar pond, and the possibility of using phase change materials as a dual-purpose layer for energy storage and insulation in the floor of the solar pond will be examine.