Abstract: Under background of "double carbon", 1 kW small-scale cooling system based on solar energy was developed in combination with rich solar energy resources and hot and dry climate conditions in Northwest China． The system took water as medium and used ultrasonic waves to atomize water into 1～5 μm clouds and mist was sprayed around the building, and building was cooled and humidified by principle of evaporation and heat absorption． Through design of photovoltaic system, power supply, control system, and water tank pipeline system, and the experimental test in a 50 m² semi-open environment, results showed that this small cooling system could reduce temperature by 6 °C on average, and humidity was 42.9%, which verified effectiveness of this system in cooling and humidifying courtyard households in Northwest China in summer．