The effect of aluminium addition to MCM-41 on product yield and carbon number distribution was investigated in the catalytic cracking of a polymer mixture, LDPE, LLDPE, and EVA copolymer, with a composition similar to that found in real agricultural film wastes. Al-MCM-41 catalyst synthesized by post-synthetic grafting method (Al-MCM-41-P) as well as Al-MCM-41 catalyst synthesized by direct sol-gel (Al-MCM-41-D). The catalytic cracking of polymer mixture was carried out in vapor phase contact as well as in liquid phase contact. The amount of acid sites increased with aluminium addition by post method as well as direct method, which was seemed to be due to Lewis acid sites. In liquid phase catalytic cracking, the yield of light hydrocarbon fraction increased with aluminium addition. The effect of aluminium addition on production of C5-C12 hydrocarbons over Al-MCM-41-P catalysts was greater than that over Al-MCM-41-D catalysts. In the case of vapor phase catalytic cracking, the effect of aluminium addition was smaller than that of liquid phase catalytic cracking. The selectivity to C13-C32 hydrocarbons was smaller in vapor phase catalytic cracking.