The current GCMs have considerable difficulty in simulating the ITCZ. Some models are prone to double ITCZ; others are just the opposite. Model tuning without the help of physical understanding does not get one very far. Thus, it is important to understand the basic physical mechanisms governing the location and intensity of the ITCZ. The importance of the SST distribution, especially its peak, to the ITCZ is well-known. In this work this factor (along with solar angle and land) is excluded so that the other factors can be studied more easily. These other factors include earth's rotation, interaction between convection and radiation, and the interaction between convection and surface fluxes. Because convection is at the center of the problem, it is expected that cumulus parameterization plays an important role in the ITCZ simulation. How these factors play their roles in the ITCZ will be discussed.