The invention discloses a shaddock peel activated carbon-chitosan adsorbent and a preparation method and application thereof. The preparation method comprises the following steps: (1) treating shaddock peel, drying to constant weight at the temperature of 100-110 DEG C, crushing to pass through a sieve with the granularity of 100-200 meshes so as to obtain shaddock peel powder, and activating the shaddock peel powder in a H3PO4 solution for 2-4 hours; (2) filtering the activated mixed solution, carbonizing the intercepted powder in a nitrogen flow at the temperature of 380-420 DEG C for 8-12 hours, so as to obtain shaddock peel activated carbon; (3) uniformly mixing the shaddock peel activated carbon and a chitosan solution, regulating the pH value of the mixed solution to be 8.5-9.5, regulating the mixed solution to be neutral after the solution is condensed, drying to constant weight at a constant temperature of 100-110 DEG C, thereby obtaining the shaddock peel activated carbon-chitosan adsorbent. The preparation method disclosed by the invention is simple, low in cost, environment-friendly and pollution-free; and compared with the traditional activated carbon adsorbent, the prepared adsorbent has better adsorption performance.