Abstract: Numerical simulations on steam condensation in the presence of air under tube bundle conditions were performed based on the software STAR-CCM+. Calculations were carried out based on a the 3 by 3 tube bundle which has a tube pitch of double diameter, aiming at recognizing local field distributions and thermal-hydraulic characteristics of various tubes. Results indicate that the air layers of various tubes interfere in the tube bundle region, forming a larger high concentration air layer region. On the one hand, this enlarges local velocity and facilitates convective heat transfer; and on the other hand increases the air layer thickness and inhibits condensation heat transfer. On the effect of bundle structure, the concentration, temperature and velocity in the tube bundle region are obviously different from those of the single tube one, sharply decreasing the local heat transfer coefficient by 50% and has a maximum variation of 1.88 times circumferentially. The axial heat transfer property mainly is affected by the development of concentration boundary layer, and circumferential heat transfer property by the adjacent tubes. By analyzing the average heat transfer coefficient, it indicates that compared to the single tube, the maximum reduction of the bundle tube average heat transfer coefficient is 9.06%.