The invention discloses a method for preparing diphenyl methane or derivatives thereof, which comprises the following steps: preparing an immobilized aluminum chloride catalyst using chitosan as a carrier, and reacting at 75-100 DEG C by using the immobilized aluminum chloride as the catalyst and benzene or derivatives thereof and benzyl chlorine as the raw materials; and after the reaction finishes, filtering the reaction liquid, and carrying out reduced pressure distillation to obtain the diphenyl methane or derivatives thereof. In the preparation process, the prepared immobilized aluminum chloride is a solid catalyst which has the advantages of high load capacity, high catalytic activity and environmental protection and can be used repeatedly; the catalyst can be recycled and used repeatedly while keeping the catalytic activity unchanged; and when the solid catalyst is used for catalyze the preparation of diphenyl methane and derivatives thereof, the amount of waste water generated by reaction is small, and the catalyst can be easily separated from the product.