Disclosed is a sliding and positioning weft catcher, comprising a frame-shaped rail (200) disposed at a weft catch end of a weaving machine. A frame-shaped optical sensor (300) is provided on the rear side of the frame-shaped rail (200). Four slide slots (220) are provided on the inner side of the frame-shaped rail (200). Two sliders (210) driven by a motor are provided in each slide slot (220). The sliders (210) oppositely disposed in the slide slots (220) are correspondingly connected by means of two pairs of parallel metal wires (100). The motor and the sliders (210) are electrically connected with the frame-shaped optical sensor (300). The metal wires (100) are driven by the motor to rotate in opposite rotation directions. In the sliding and positioning weft catcher, when the frame-shaped optical sensor detects that a weft passes through the weft catcher, the motor starts, and the sliders drive the parallel metal wires to quickly move toward each other from edges of the frame-shaped rail. As the quadrilateral defined by the four parallel metal wires becomes smaller, the weft is finally limited at the center of the frame-shaped rail. Moreover, since the parallel metal wires oppositely rotate inwards, the weft can be tensioned and prevented from coming off.