The invention discloses a device for providing an optical nipper with momentum, which is used to provide an optical nipper with first momentum in a detection test member. The invented device comprises a laser source, a diffractive optical element (DOE) and a lens. The laser source is used to output laser. The DOE has a phase delay graph. The laser generates a diffractive graph after passing the phase delay graph. The lens receives the diffractive graph and focuses it on the detection test member to form an optical nipper with first momentum. Wherein the lens has an optical axis which intersects with the DOE at the optical axis intersection point. The geometric centre of the phase delay graph has a displacement vector with respect to the optical axis, and the direction of the first momentum relates to the direction of the displacement vector.