The invention discloses an in-situ fluoride adsorption method from a waste lithium battery via high-ferro slag. According to the method, the high-ferro slag serves as an adsorbent to absorb fluoride released in the high-temperature thermal decomposition process of an organic binder of polyvinylidene fluoride in an anode piece of the waste lithium battery. Compared with the prior art, in the method, the industrial solid waste can be converted into a functional material capable of in-situ fluoride adsorption, the difficulty in stacking the industrial solid waste is overcome, the industrial solidwaste is reduced, made into resource and made harmless, and the in-situ adsorption rate for fluorine in the polyvinylidene fluoride of high-ferro slag is as high as 99.0wt% and even higher.