The carbon (C) cycle in rubber plantations, which are located in a suitable planting region (altitude 550-600 m) in Xishuangbanna, was simulated using the Biome-BGC model for the period 1959-2012. We obtained the following results. (1) Compared with the actual measurements, the accuracy was 98.37% and 90% for the simulated annual gross primary productivity (GPP) and total respiration (Rt), respectively. Because of an underestimate of GPP and an overestimate of Rt, the simulated annual net ecosystem exchange (NEE) was 157.35 g C m^-2 a^-1 lower than the measured value. However, the accuracy was greatly enhanced when dry rubber C stock (139 g C m^-2 a^-1) was taken into account. (2) During the initial 8 years, rubber plantation acted as a C source because of the higher heterotrophic respiration rate, with an average simulated NEE of 357 g C m^-2 a^-1. Subsequently, however, the balance changed to C sequestration, with an average simulated NEE of -146 g C m^-2 a^-1. (3) Rubber plantation sequestrated 1 835 g C m^-2 during a 40-year rotation length, which is lower than that in tropical rain forests, which fixed 6 720 g C m^-2 a^-1 during the same period, indicating that rubber plantations established in areas of former tropical rain forest might lead to C release, even during a complete life cycle. These results enabled us to gain a better understanding of the impact of rubber plantation on the local carbon cycle. In order to reach a sustainable balance between the regional economy and environmental protection, it is suggested that the local government should not only regenerate older rubber plantations in a planned way to maintain C balance in the rubber plantation ecosystem, but also pay considerable attention to the protection of tropical rain forests.