The deacidification of Liaohe straight-run diesel with combination solvent in the alcohol-ammonia process was carried out. Effects of solvent composition, demulsifier type and amount and the operating conditions on the deacidification ratio and the yields of diesel were all studied. The suitable mass composition of solvent mixture is 5% NH ₃·H ₂O, 50% ethanol, 45% water and 0.4 μL NP6 demulsifier for 20 mL diesel. Operating conditions are as followings, the volume ratio of solvent to diesel 0.2, the treatment temperature 50 ℃, the processing time 60 seconds and the phase separation time is 20 minutes. The acid value of the diesel after deacidification comes up to the standard GB/T264-83 (acid value<5 mg(KOH)/(100 mL)). The solvent can be recycled by distillation and no waste generates, the naphthenic acid can be obtained by heating the distillation residues.