In this paper, the degradation of unsym-dimethylhydrazine wastewater with low atmospheric plasma generated by floating-electrode dielectric barrier discharge was studied, and the treatment conditions were optimized. Firstly, the degradation effects of low atmospheric plasma equipment, xenon lamp and ultraviolet lamp were compared. Secondly, the influence of discharge gap, initial solution pH, treatment time, addition of sodium hydroxide solution were also studied. Meanwhile, the effect of low temperature plasma on the pH value of unsym-dimethylhydrazine wastewater was also investigated. Without the addition of other reagents, the degradation of unsym-dimethylhydrazine with low temperature plasma was better than xenon lamp and ultraviolet lamp. When the discharge gap was shortened from 4 mm to 2 mm, the degradation rate of unsymdimethylhydrazine was increased by 47.2%. With the increase of plasma treatment time, the content of unsymdimethylhydrazine decreased, and 82.1% of unsym-dimethylhydrazine could be degraded after treatment for 20 minutes. The pH value of the unsym-dimethylhydrazine wastewater decreased from 10 to 6.9 after 10 min of treatment. While, the degradation rate of unsym-dimethylhydrazine increased by 65.9% with the initial pH value increased from 2 to 10. After 10 min of low temperature plasma treatment, sodium hydroxide solution was added to the wastewater with a concentration of 1 mg/mL, and the degradation rate of unsym-dimethylhydrazine reached 95% after another 10 min treatment.