A four-wheel drive control system is provided which comprises a driving force distribution mechanism for transmitting a driving force from a power source to main driving wheels of a vehicle and capable of distributing the driving force to auxiliary driving wheels of the vehicle, a rotational speed difference detector for detecting a rotational speed difference between the main and auxiliary driving wheels, and a driving force distribution controller for controlling a distribution of the driving force to the main and auxiliary driving wheels on the basis of the rotational speed difference, wherein the driving force distribution controller determines a driving force to be transmitted to the auxiliary driving wheels on the basis of an output of the power source, a longitudinal load distribution in the vehicle and the rotational speed difference. A four-wheel drive control method is also provided.