The invention discloses a detachable filter element, a filter flask and a water purifier adopting the detachable filter element. The detachable filter element comprises membrane filaments, a cylindrical filter element casing used for accommodating the membrane filaments as well as a fixing seat which is connected with one end of the filter element casing and used for fixing the membrane filaments, wherein a detachable structure is formed between the fixing seat and the filter element casing. The filter flask comprises a mounting seat and a filter flask casing, wherein the mounting seat and one end of the filter flask casing are in detachable seal connection to form a cavity for mounting the filter element, and the filter element adopts any one of detachable filter elements. The filter element is changed into a detachable structure, the filter element casing and the fixing seat can be dismounted to expose the inside membrane filaments, the dirty membrane filaments can be repeatedly cleaned and continuously used within life duration of an ultrafiltration membrane, and accordingly, the use cost of the water purifier is reduced.