The invention, which relates to the technical field of gap detection of a cement paste mixer, discloses a special-purpose needle gauge for measuring the gap of a cement paste mixer. The special-purpose needle gauge comprises a first needle body, a connecting steel wire, a second needle body, a support sleeve, a fixation ring, a grouting hole, a support seat, a return spring, a limiting plate, a connecting rod, a bearing plate, a limiting ring, a fixation groove, a clamp slot, a handle, and a clamping block. One end of the left side of the connecting steel wire is fixedly connected to the center of the right side of the first needle body; and one end of the right side of the connecting steel wire is fixedly connected to the center of the left side of the second needle body. According to thespecial-purpose needle gauge, with the first needle body and the second needle body matching the curved surface of the inner wall of the agitating pan, the spacing between the inner wall of the agitating pan and the fan is calibrated conveniently; the fused brazing filler metal is injected into the inside of the support sleeve through an injected hole; and the first needle body, the connecting steel wire, and the second needle body are connected closely and stably through brazing.