In subtropics, the higher energy consumption of air conditioning system in summer period brought about the application of task/ambient air conditioning (TAC) systems, not only in commercial buildings, but also in residential buildings. To better assess the performance of the TAC system, a numerical study was carried out to predict the energy and thermal performance of a bedroom TAC system in a bedroom in subtropical area. To conveniently predict the indoor thermal environment, response surface methodology (RSM) was applied to simplify the procedure of numerical simulation. Firstly, CFD study was carried out to evaluate the thermal and energy performance of the TAC system. Secondly, RSM method was used to establish the predictive models of important index of indoor thermal environment to form the simplified numerical method. Thirdly, these two methods were used and the predicted values were compared. It was found that the energy consumption was reduced from 260 to 160W when the is was increased from 19 to 23 degrees C, and the averaged draft risk (DRoz) reached at 20% when the Q(s) was set at 110 1/s. The significant vertical non-uniformity of air temperature, air velocity and relative humidity were also reported. Besides, the CFD method was compared with the simplified numerical method (RSM method). It was found that the maximum deviation between using the RSM and CFD methods was less than 5% in predicting energy consumption, draft risk, thermal parameters in the occupied zone, stratified air temperature and stratified air relative humidity. Overall, the simplified numerical method (CFD based RSM method) can predict the indoor thermal environment accurately. (C) 2018 Elsevier B.V. All rights reserved.