The cooling heat transfer performance and change regulation of secondary flow of supercritical CO₂ whose mass flow rate varies are studied in horizontal elliptical tube whose torque is 100mm or one infinity number based on Fluent. And the influence of axial ratio and torque of twisted elliptical tube on the heat transfer performance is studied. Simulation results show that, the effect of buoyancy on the twisted elliptical tube is significantly larger than that of elliptical tube under low mass flow, for the elliptical tube when supercritical CO₂ is under the low mass flow , the elliptical tube has a greater intensity of secondary flow caused by buoyancy, and the enhanced heat transfer is more pronounced, when supercritical CO₂ is under the high mass flow , the twisted elliptical tube has a greater intensity of periodic secondary flow caused by self-structure, and the enhanced heat transfer is more pronounced. The heat transfer coefficient and pressure drop increase with the degree of twist and flattening.