In this study, the impacts of different numbers of Cloud Condensation Nuclei (CCN) on the Tropical Cyclone (TC) development was investigated by using idealized numerical simulation. It is found that, the larger CCN inhabits TC development. Namely, the TC has a weaker intensity but larger outer size, which agrees with the previous studies. However, this impact is highly sensitive to the environmental moisture condition. Under a moist ambient condition, the impacts of CCN are much pronounced. In a dry environment, the influence of CCN is quite weaker. This suggests that the moisture is vital to the TC development, which is should be taken into consideration the cooperative impacts of CCN and moisture in the operational forecasting.