Abstract: During the rolling process, there is cracking in the some parts of 27SiMn seamless steel tubes for hydraulic supports. The chemical composition of the steel tube was checked, and the microcosmic analysis was conducted by metallurgical microscope and electric scanning microscopy. It is concluded that nonmetal inclusions in the continuous casting billet destroyed the structural succession of the material, and microcracks formed in this zone because of uneven stress during the rolling process. The high-speed of elevated temperature during the reheating process, increases the temperature gradient in the radial direction, tangential pulling stress forms at the outer surface because of the volume contract produced by the microstructure transform, and microcrack propagation leads to the local cracking of the tube. The paper qualitatively analyzed the inclusions, traced back to the source and provided appropriate measures for improvement.