The ecological environment over Central Asia which is characterized by semi-arid and arid climates is highly fragile and very sensitive to climate change. It is necessary and valuable to improve the climate models performance over Central Asia for policy makers to make policies and take actions in response to the climate changes in the future. In this study, based on the output of the CMIP5 historical experiment during 1948-2011, the performance of Beijing Climate Center Climate system model(BCC_CSM)with different horizontal resolutions (BCC_CSM1.1 with coarse resolution and BCC_CSM1.1m with fine resolution)in simulating the summer precipitation over Central Asia during 1948-2011 was evaluated and the possible causes related to the impact of horizontal resolution on the models performance were also further analyzed and discussed. Results show that increasing horizontal resolution can obviously improve the simulation of inter-annual variability and long term trends of summer precipitation over Central Asia, but has limited improvement in simulating the climatic mean precipitation over the entire Central Asia and western Central Asia. Compared with BCC_CSM1.1 model, BCC_CSM1.1m shows much higher improvement in simulating the climatic mean, inter-annual variability and long term trends of summer precipitation over east Central Asia than over west Central Asia. Meanwhile, BCC_CSM1.1m model shows better performance in simulating the long term trends of convective and large scale precipitation, climatic mean and inter-annual variability of large scale precipitation as well. However, increasing model horizontal resolution tends to deteriorate the convective precipitation simulation. Overall, the improvement of the summer total precipitation simulation over Central Asia in the BCC_CSM1.1m model with finer horizontal resolution is attributed to the improved large scale precipitation simulation, compared with BCC_CSM1.1 model. Further mechanism analysis suggests that increasing model horizontal resolution can contribute to the improvement of the simulated westerlies at 200 hPa level and the atmospheric circulations at 850 hPa level, which leads to a better simulation of the summer precipitation over Central Asia in BCC_CSM1.1m model than that in BCC_CSM1.1 model.