Abstract　 　　 

　Prominences in the million degree solar corona are hundredfold cooler and denser than their surroundings. The formation of a solar prominence within a coronal cavity has been detected by recent the Atmospheric Imaging Assembly instrument (AIA) onboard the Solar Dynamics Observatory (SDO) satellite observations. A bright emission cloud shifts the peak brightness progressively from hot channels to cool channels, which shows evidence of plasma cooling and condensation during prominence formation. Despite detailed observations, we still lack insight on how this material collects into large-scale prominences. In order to study prominence plasma formation in realistic magnetic configurations, we perform three-dimensional magnetohydrodynamic simulations considering thermodynamics in the solar corona including radiative cooling, anisotropic thermal conduction, and parameterized coronal heating, started from a numerical isothermal magnetic flux rope from our previous work. Due to excess density inside the flux rope, runaway radiative cooling causes a dramatic drop of temperature leading to plasma condensation in the middle dipped region of the flux rope. The cool dense condensation forms a slab-shape prominence stably supported by dipped field lines while the density depletion in the rest part of the flux rope creates a coronal cavity. We generate AIA synthetic views of our simulated prominence-cavity system and validate our model with many similarities with observations, e.g., the overall three-part structure and detailed structures like horns and barbs.