Abstract: The structure and components of a newly-designed small-sized modularized seawater desalination system powered by solar energy with multi-effect heat recovery units were introduced in detail. Through tests under different weather conditions and in different pressure regulating ways, the freshwater yield of the solar seawater desalination system was analyzed, thus obtaining the ways to improve the performance ratio and total efficiency of the system. Results show that via the free pressure setting method to regulate the steam pressure, and by controlling the maximum collecting temperature at 130 °C, the freshwater yield of unit collecting area in the modularized system with about 2.31 m² daylight gathering area can reach 1.982 kg/(h·m²), and the all-day freshwater yield is up to 7.869 kg/m², with a highest performance ratio up to 2.5, the total efficiency up to 1.35, and the system collecting efficiency up to 0.4, indicating outstanding performance of the solar seawater desalination system.