Based on axial compression test of 40 super high-strength concrete filled in circular steel tube,super high-strength concrete with circular steel tube as a composite material was studied.The calculation formulas for theoretical parameters(ultimate strength,plateau strength and peak strain) for super high-strength concrete with circular steel tube are establishad.Through comparing,it is pointed out that the existing calculation formula does not fit to the super high-strength concrete with circular steel tube.A tri-curve equation for stress-strain curves of the super high-strength concrete with circular steel tube is presented and it is in good agreement with the curve obtained from measurements.