A filter quick knockdown mechanism for positioning a filter in a housing of a household water purifier, the filter quick knockdown mechanism comprising: a first positioning mechanism configured to be arranged on the filter; a second positioning mechanism configured to be arranged on the housing; and a locking mechanism, wherein the first positioning mechanism comprises a guide groove or a positioning protrusion configured to mate with a corresponding positioning prostrusion or guide groove of the second positioning mechanism respectively, and wherein, when the first positioning mechanism and the second positioning mechanism are mated with each other, the guide groove and the positioning prostruction are both parallel to an axis of the filter, and the filter is configured to couple with the housing via the locking mechanism, wherein, the locking mechanism comprises snapping blocks and a translation rod, the translation rod is configured to be slidably arranged on the housing, an upper end of the filter is provided with a connection boss for connecting a water flow pipeline, and the translation rod and the connection boss each are provided with the snapping blocks at equal intervals, when the connection boss is abutted against a bottom surface of an inner cavity of the housing, ones of the snapping blocks which are arranged on the translation rod are coupled with ones of the snapping blocks which are arranged on the connection boss, so as to lock the filter; wherein the connection boss comprises two symmetrical side surfaces, the translation rod is a Y-shaped translating fork, two branches of the Y-shaped translating fork are symmetrically arranged at the two side surfaces of the connection boss, the two branches of the Y-shaped translating fork each are connected with a first spring, characterized in that, a handle portion of the Y-shaped translating fork is connected with a linkage mechanism which is provided at top thereof with a recess with a gradually changing depth, and the handle portion of the Y-shaped translating fork is abutted against the recess, such that the Y-shaped translating fork is moved inward as the linkage mechanism is moved upward. a first positioning mechanism configured to be arranged on the filter; a second positioning mechanism configured to be arranged on the housing; and a locking mechanism, wherein the first positioning mechanism comprises a guide groove or a positioning protrusion configured to mate with a corresponding positioning prostrusion or guide groove of the second positioning mechanism respectively, and wherein, when the first positioning mechanism and the second positioning mechanism are mated with each other, the guide groove and the positioning prostruction are both parallel to an axis of the filter, and the filter is configured to couple with the housing via the locking mechanism, wherein, the locking mechanism comprises snapping blocks and a translation rod, the translation rod is configured to be slidably arranged on the housing, an upper end of the filter is provided with a connection boss for connecting a water flow pipeline, and the translation rod and the connection boss each are provided with the snapping blocks at equal intervals, when the connection boss is abutted against a bottom surface of an inner cavity of the housing, ones of the snapping blocks which are arranged on the translation rod are coupled with ones of the snapping blocks which are arranged on the connection boss, so as to lock the filter; wherein the connection boss comprises two symmetrical side surfaces, the translation rod is a Y-shaped translating fork, two branches of the Y-shaped translating fork are symmetrically arranged at the two side surfaces of the connection boss, the two branches of the Y-shaped translating fork each are connected with a first spring, characterized in that, a handle portion of the Y-shaped translating fork is connected with a linkage mechanism which is provided at top thereof with a recess with a gradually changing depth, and the handle portion of the Y-shaped translating fork is abutted against the recess, such that the Y-shaped translating fork is moved inward as the linkage mechanism is moved upward.