The invention discloses a method for preparing a modified macadamia shell adsorbent. According to the method, a waste biologic material, macadamia shells, is taken as a raw material, pollutants on the surface of the adsorbent can be cleaned by pretreatment, carboxyl on the surface of the adsorbent can be increased by acid treatment, and amino on the surface of the adsorbent can be increased by ethidene diamine. The preparation method is simple in preparation technology and low in cost; the obtained adsorbent has the advantages of being large in specific surface area, good in chemical stability, high in mechanical strength, easy in regeneration, and the like, and has a good effect of removing dye waste water, thus having great application value.