The invention discloses a pretreating method for high-salinity wastewater generated in preparation of hydrazine hydrate through a ketazine method. The hydrazine hydrate wastewater is subjected to stripping treatment, the wastewater obtained after stripping treatment is subjected to ultrafiltration treatment, the wastewater produced through ultrafiltration treatment enters a next working section to be treated, and trapped fluid is subjected to slag treatment. According to the pretreating method, the hydrazine hydrate wastewater is pretreated through stripping and active carbon and membrane coupling, and the advantages of being low in energy consumption, simple in process, reliable in result and the like are achieved.