Abstract: The key point of cold-drawing of internal straight-ribbed steel tubes for heat-exchanger lies in the fact that along with the rib height is increased, the rib itself is compressed. Based on the experiments, the article analyses the influence on both increase and compression of rib height by such factors as wall-thickness compression at the bottom of the rib （ε％）, wall thickness to diameter ratio（δ₀/D₀） , plug groove to rib height ratio （K） and friction conditions etc. and relevant relationship.