The invention provides a method for extracting bromelain ananase through a chitosan carboxylation derivative, which comprises the following steps of: (1) preparing the chitosan carboxylation derivative; (2) carrying out preprocessing on pineapple juice; (3) adsorbing the bromelain ananase; (4) eluting the bromelain ananase; and (5) refining and drying the bromelain ananase. The method for extracting bromelain ananase through the chitosan carboxylation derivative has the advantages that: (1) the obtained enzyme has high activity, and is safe and reliable; (2) the process has less pollution to an ultrafiltration membrane, and the production efficiency is high; (3) the production of the bromelain ananase is not limited by pineapple harvest time; (4) two products of the bromelain ananase and the pineapple juice can be obtained simultaneously; and (5) the process is flexible, the bromelain ananase can be collected through ultrafiltration or salting out, and when the salting out method is used, the volume of the bromelain ananase solution is only 1/20 of the original pineapple juice, so that the used salt is greatly reduced.