The invention discloses a degradable starch-degradable chromium-containing leather pulp composite as well as a preparation method and application thereof. The preparation method is characterized by comprising the following steps of: adding 80-100 parts of degradable starch, 60-80 parts of degradable chromium-containing leather pulp, 10-15 parts of hydrochloric acid with concentration being 12mol / L, 80-100 parts of water and 20-25 parts of 25-30%hydrogen peroxide into a reactor with a stirrer, stirring and reacting for 1-3hours at 85-95 DEG C; cooling the reactants to 50 DEG C, slowly adding 3-5 parts of sodium hydrogen sulfite, stirring and reacting for 1-2hours so that the reaction pulp is completely dissolved in water, and then cooling to 25 DEG C; adjusting the pH value of the reactant pulp to 4.0-5.0 by using a NaOH solution, stirring and reacting for 1-2hours, to finally obtain the degradable starch-degradable chromium-containing leather pulp composite. The problems that in the existing preparation process, starch is not modified uniformly, the oxidization selectivity is poor and production cost is high are solved. After the degradable starch-degradable chromium-containing leather pulp composite is used as leather filler for filling leather, the filled leather is thickened obviously and has high physical mechanical strength, soft and full handfeel, and therefore, the degradable starch-degradable chromium-containing leather pulp composite has excellent filling effect.