A detachable filtering apparatus for an air conditioning system and an installment method thereof provides an air disinfection function. It can be operated continuously, is suitable for conventional air conditioners and is applied at a place that requires disinfection. A hollow circular frame and a multi-aperture filter screen are detachably installed at a specified installation area of the air tube of the air conditioning system. The structure of the filtering apparatus can be installed easily and conveniently and is suitable for adjustable air pipes. It is convenient to maintain the air conditioner.