Disclosed is a tensioning device on a pre-tensioning flow unit production line for a track slab on a high-speed rail, wherein ground supports (107) at a fixed height support a tensioning bed by means of universal balls; a tensioning power mechanism is fixed on the tensioning bed; track slab production line transport tracks (106) are arranged on a ground surface at inner sides of the ground supports (107); and track slab positioning supports (104) are arranged at two sides of the transport tracks (106). The device solves the problems in the prior art of low degree of automation, complex tensioning mould emplacement, and poor positioning and tensioning precision, etc.