The invention discloses a solar pneumatic pump automatic watering device which comprises a pneumatic pump water container, a 
check valve, a 
water storage container and a water retaining container. The 
check valve is used for controlling the 
water flow direction to form a water inlet pipeline and a water outlet pipeline; air in the pneumatic pump water container expands with heat and contracts with cold to generate air 
pressure difference to achieve 
water pumping, water flows in from the 
water storage container through the water inlet pipeline when the interior of the pneumatic pump water container is in negative pressure, the water flows out to the water retaining container through the water outlet pipeline when the interior of the pneumatic pump water container is in 
positive pressure, and the pneumatic 
water pumping process is formed; and the 
water level in the water retaining container rises to trigger a 
siphon drainage process, and the 
water level descends to finish the 
siphon drainage process. Along with the alternation of day and night, the temperature in the pneumatic pump water container circularly changes in a reciprocating mode, 
water flow is continuously pushed to flow from the 
water storage container to the water retaining container, and automatic 
water pumping, water storage and periodic watering are achieved. The device is simple, practical, free of 
power consumption, energy-saving, environment-friendly and stable and reliable in operation, and existing resources and wastes can be fully utilized.