Steel bar connecting sleeve for the site construction, bridges, roads, etc., with high joint strength, connection speed, strong applicability, the construction efficiency is high. Section material energy saving economy and so on. The mechanical properties and chemical composition of the carbon structural steel with no less than 45, the mechanical properties and chemical composition of the GB699 standard, the standard value of the bending strength and tensile strength of the sleeve is 1.10 times higher than that of the corresponding bearing capacity.