The invention relates to the field of seawater desalinization, in particular to a wind-power complementary pneumatic seawater desalting device, which comprises a pneumatic water pressure booster pump, an electric water pump, a gas pipeline and a wind-driven air compressor unit. The air compressor unit comprises a cabin, a wind turbine impeller mounted in the front part of the cabin, and an impeller main shaft, an accelerating gearbox, a coupler and an air compressor fixedly connected with each other in sequence and mounted in the cabin. Output compressed air of the air compressor is communicated with the pneumatic water pressure booster pump via the gas pipeline. The air compressor is driven directly by wind power to generate the compressed air, and the compressed air is used as the main power of the pneumatic water pressure booster pump for performing seawater reverse osmosis desalination; and when the wind power is inadequate or no wind exists, the electric water pump can be startedproperly to pressurize in order to guarantee the operation of a seawater desalting facility. The invention is applied to reverse osmosis seawater desalination and reduces the electric energy consumption, and has the advantages of saved investment, high efficiency, low operation and maintenance cost and the like, and is particularly suitable for many islands and coastal areas.