A system for guiding execution of a main function of a vehicle, includes an input unit, a storage, a display and a controller. The input unit includes an independent function key configured to independently perform a function, and a dependent function key capable of performing a function when being selected in connection with another key. The storage stores vehicle state information indicating a state of the vehicle and explanation information about a dependent function key corresponding to error information. The display is configured to display guide information. The controller is configured to output, through the display, an input value of the dependent function key and explanation information corresponding to the vehicle state information by referring to the storage when the dependent function key is inputted two or more times while a condition for operating the dependent function key is not satisfied.