The paper numerically studies the air flow and heat transfer characteristics for a spiral tube air-fuel heat exchanger used in an aero-engine, analyzes and compares various turbulence models and compares the obtained results with existing correlations, discusses the difference of air flow and heat transfer under constant and variable air physical properties, and analyzes the changes of flow and heat transfer along the flow direction as well as the effect of helix angle. The results show that: when the air flows across the spiral tube bundle, the heat transfer coefficients of the first and last tube rows are smaller than those of the middle tube rows, whereas the pressure drop of the first tube row is the largest and that of the last tube row is the smallest; the helix angle has little effect on the heat transfer coefficient, and the pressure drop tends to decrease with the increase of the helix angle.