The invention discloses a chemical pretreatment method and a device thereof for treating high-salinity wastewater and belongs to water treatment technologies. The device comprises an adjusting tank, a pipeline mixer, a sedimentation tank, a V-shaped filter tank and ion exchange resin. The method comprises the following steps: adjusting the high-salinity wastewater in the adjusting tank; mixing the wastewater with sodium hydroxide and carbon dioxide in the pipeline mixer, and then putting the mixture into the sedimentation tank; after reacting for a certain period of time, removing solid suspended matters, hard substances and part of COD (chemical oxygen demand) pollutants from water by virtue of high-efficiency flocculation and sedimentation, and leading a supernatant into the V-shaped filter tank; and putting the high-salinity wastewater obtained after filtration in the V-shaped filter tank into an ion exchange resin softening system, and performing further softening treatment on the high-salinity wastewater. According to the technology, the combination of carbon dioxide and sodium hydroxide is adopted to ensure a good hardness removal effect, reduces the surrounding dust pollution to the utmost extent, and greatly reduces the cost of chemicals.