The invention discloses working 
electrolyte of a 650V-700V extra-high-
voltage aluminum electrolytic capacitor. The working 
electrolyte of the 650V-700V extra-high-
voltage aluminum electrolytic capacitor comprises, by weight, 45-65% of primary solvents, 5-20.5% of secondary solvents, 10-20% of solutes, 8-25% of spark 
voltage improvers, 5-10% of stabilizers, 0.2-3% of 
hydrogen absorbents, and 2-5% of other additives. The invention further discloses a preparation method of the working 
electrolyte of the 650V-700V extra-high-voltage 
aluminum electrolytic capacitor and the 650V-700V extra-high-voltage aluminum 
electrolytic capacitor. According to the 650V-700V extra-high-voltage aluminum 
electrolytic capacitor, the working electrolyte and the preparation method of the working electrolyte, the spark voltage improvers and the stabilizers within the reasonable ranges are used, the high-voltage resistance and high-
temperature resistance of the electrolyte are improved, and meanwhile the working electrolyte has low gas production performance. When the aluminum 
electrolytic capacitor with the electrolyte is subjected to a 
ripple current 
life test at 85 DEG C for 2000 hours, the aluminum electrolytic 
capacitor can 
resist the voltage of 650-700V and even higher voltage, and a 
breakdown phenomenon caused by unstable spark voltage of the electrolyte is avoided.