The invention discloses an improved roots vacuum pump which comprises a shell, a rotor cavity, an inner sleeve and a cooling cavity, wherein a partition plate is connected in the cooling cavity; the cooling cavity is divided by the partition plate into a first cooling water channel on the inner side and a second cooling water channel on the outer side; the first cooling water channel is connectedto a water inlet in a penetrating manner; the second cooling water channel is connected to a water outlet in a penetrating manner; a cylindrical cavity is formed in the bottom of the cooling cavity; aresidue storage tank is connected below the cylindrical cavity in a penetrating manner; a rotary shaft is inserted into the cylindrical cavity; a rotary knob is connected to the outer side of the rotary shaft; the part, located on the inner side of the cylindrical cavity, of the rotary shaft is connected to a first metal frame; a second metal frame is also connected to the rotary shaft; the second metal frame and the first metal frame are mutually perpendicular, an arc-shaped panel is fixedly connected to the outer side of the second metal frame, brushing hairs are connected to the outer sideof the arc-shaped plate, and an arc-shape screen is connected to the outer side of one end of the first metal frame. According to the improved roots vacuum pump disclosed by the invention, defects inthe prior art can be improved, and blockage of the cooling water channels as a result of metal residues of the cooling cavity of the pump can be prevented.