The utility model relates to a seawater desalination ultrafiltration membrane chemical enhancement backwashing device which comprises a water source assembly, a dosing assembly and an ultrafiltrationassembly, and the ultrafiltration assembly comprises an ultrafiltration backwashing water inlet valve, an ultrafiltration backwashing upper discharge valve, an ultrafiltration water inlet valve, an ultrafiltration water production valve and an ultrafiltration device; the ultrafiltration device is respectively connected with an ultrafiltration water inlet valve and an ultrafiltration backwashing upper discharge valve; the ultrafiltration backwashing water inlet valve is connected with the ultrafiltration water production valve, and the first water outlet is connected between the ultrafiltrationbackwashing water inlet valve and the ultrafiltration water production valve; wherein the water source assembly is connected to the pipeline mixer, the dosing assembly is connected to the pipeline mixer, and the pipeline mixer is connected with an ultrafiltration backwashing water inlet valve in the ultrafiltration assembly. According to the chemical enhanced backwashing device for the sea waterdesalination ultrafiltration membrane, provided by the utility model, by arranging the special pipeline, the step sequence is optimized, the dosing time and the dosing amount are reduced, unconsumed chemicals remained in the pipeline are reduced to the greatest extent, the treatment pressure after waste liquid is discharged is reduced, and the influence on the environment is greatly reduced.