The invention relates to a positioning mechanism for transport, which comprises a fixed plate, an air cylinder, a holding jaw, fine-adjustment mechanisms and a control circuit, wherein the air cylinder, the holding jaw and the fine-adjustment mechanisms are all mounted on the fixed plate; a transverse spout is arranged on the fixed plate; the holding jaw is provided with at least one connected in the transverse spout through sliding connection of a slide block; the holding jaw is driven to slide from left to right in the transverse spout by connection of the air cylinder and the slide block; the number of the fine-adjustment mechanisms for limiting the holding jaw is two, and the two fine-adjustment mechanisms are fixed at the two ends of the transverse spout; the fine-adjustment mechanisms include millesimal measuring heads and buffers arranged parallel; heads of the two fin-adjustment mechanisms are arranged oppositely and towards the slide block; the holding jaw has two working positions; when in a first working position, the holding jaw is arranged at the left end of the transverse spout; and when in a second working position, the holding jaw is arranged at the right end of the transverse spout, and a top supporting air cylinder for clamping the workpiece held by the holding jaw is fixedly connected on the holding jaw. The positioning mechanism for transport has high responsiveness and low energy consumption and achieves the effect of accurately positioning the holding jaw.