Abstract: This experiment is to investigate the condensation heat transfer characteristic of vertical tube bundle by controlling the steam parameters in vertical tubes immersed in head water tank. To explain the phenomenon of a sharp decline of condensation heat transfer coefficient and the difference of condensation heat transfer characteristics between center tube and side tube, the growth rate of condensate and condensation thermal resistance were analyzed detailedly. The experimental results show that the condensation heat transfer coefficient of tube bundle is significant better than that of single tube, especially the condensation heat transfer coefficient of the center tube is much better than that of side tube under the same steam conditions. Through the contrast of heat transfer coefficient of the test value and the calculated values of both the classical and the modified Nusselt theories, the results show that the test value of center tube accords well with the calculation value of the modified Nusselt theory, but the deviation of side tube is larger.