The physical model and mathematical model of solar refrigeration and desalination co-generation system were established. The performance and economy of the system were analyzed by changing the three variables of refrigeration capacity, seawater desalination effects number and three different cities. The results show that increasing refrigeration capacity is conducive to improving freshwater production and increasing freshwater efficiency, but more auxiliary heat consumption is needed, the comprehensive effect is to shorten the recovery period. Increasing desalination efficiency is conducive to increasing freshwater production and freshwater efficiency, and the auxiliary heat consumption remains unchanged. The comprehensive effect is to shorten the recovery period. Solar energy is the main energy needed in the co-generation system of the three cities, and Shenzhen has the largest proportion of energy supply, which reaches 67.8%. Compared with the solar refrigeration system, the recovery period of the co-generation system can bu shortened by 18.1%.