Abstract: XRD analysis was used to understand the phase composition of waste cathode carbon block in aluminum electrolysis. After that, water leaching was done repeatedly and then the electrolyte leaching situation of the block was studied by the number and temperature of water leaching. Waste cathode carbon particles of 1 ~ 2 mm were used for each experiment of water leaching, under the condition of solid-liquid mass ratio of 1:5. The water leaching solution and carbon particles were obtained through filtration, and the crystallized water leaching solution was evaporated for phase analysis. The experimental results showed that the evaporation crystallization amount of waste cathode carbon in the aluminum electrolysis increased with the increase of temperature, the evaporation crystallization amount of the first leaching was the highest, and the percentage of fluorine in the evaporation crystallization of the second one increased. After the leaching temperature was increased by 30 ℃, the fluorine content of the first leaching was the sum of the first and the second leaching before the temperature rise. F, Al and Na had the best leaching effect at 130 ℃.