Abstract: This is an essay in the field of metallurgical engineering. The effects of crushing particle size and leaching conditions on the leaching of lithium cobalt from spend lithium-ion batteries in the citric acid environment were studied, which provided some reference for the recovery of different types of mixed spend lithium-ion batteries. The results showed that Mn, Al, Ni, Co and Li accounted for a large proportion of the contents in mixed different types of spend lithium-ion batteries. Due to the larger recovery value of Co and Li and simplify the recovery process, only Co and Li be recovered. The crushing particle size has little influence on the leaching rate of lithium cobalt in the range of -5 mm, while the leaching rate of lithium cobalt in the larger crushing particle size is not high, which may be lithium and cobalt wrapped in the middle of particles and cannot contact with the leaching solution, thus reducing the leaching effect. For mixed different types of spend lithium-ion batteries, under the conditions of -5 mm particle size, citric acid concentration 1.0 mol/L, leaching temperature 65 ℃, solid-liquid ratio 1 g/100 mL, H₂O₂ concentration 3%, leaching time 55 min, stirring speed 30 r/min, the lithium leaching rate of 97.86% and cobalt leaching rate of 98.01% are obtained.