The invention provides a filter for casing. The filter comprises a flow inlet, an upper liquid storing area, a lower liquid storing area, a filter screen groove, a window, a sticky core and a flow outlet, wherein the flow inlet is formed in the top of the filter and used for guiding molten iron into the filter; the upper liquid storing area and the lower liquid storing area are arranged below the flow inlet and used for reducing flow speed of iron liquid and enlarging the contact area between the molten iron and a filter screen, the filter screen groove is formed between the upper liquid storing area and the lower liquid storing area, the cross section of the filter screen groove is rectangular, the boundary size of the filter screen groove is larger than the section size of the liquid storing areas, the filter screen groove is used for bearing a filter screen, the window is arranged on the side face of the width direction of the filter screen groove, and used for inserting the filter screen into the filter screen groove, the sticky core is installed on the window in a clearance fit manner, the flow outlet is formed in the lower portion of the lower liquid storing area, the flow outlet and the flow inlet are distributed symmetrically with the filter screen groove as an axis, and the flow outlet is used for connecting flow input points of a casting cavity. A filtering system utilizes the multiple filters to be combined in many forms to be suitable for producing castings of different structure shapes and various weights.