A rustproof treatment method for a lithium ion battery steel shell, comprising: cleaning the residual electrolyte on the surface of the battery with clean water; immersing the cleaned battery in the passivation diluent for 1 minute to 1 minute and 30 seconds, waiting for the battery steel shell A passivation protective film is formed on the surface, and the battery is taken out and cleaned again with water; finally, the battery is immersed in alcohol and washed and then dried; the above passivation solution is formulated: sodium citrate 1-3% by weight, sodium molybdate 1-3%, 5-9% phosphoric acid, the rest are water, and the passivation solution and water are further diluted at a ratio of 1 to 5-7 by volume; the advantage is: through the steel shell of the battery Large-scale anti-rust treatment can significantly improve the anti-rust effect of the battery steel shell, prolong its long service life, and improve the production efficiency of the battery.