A control system of a vehicle automatic transmission in which an engine load and a vehicle speed are detected and used to determine a vehicle acceleration in accordance with the preestablished characteristics. An actual vehicle acceleration is at the same time calculated in response to the detected vehicle speed. The difference therebetween is then calculated and the calculated value is added to a difference calculated earlier to obtain an average therebetween. Five gear shifting scheduling maps, for example one for moderate hill climbing, one for level-road running, one for steep hill descent, are preestablished and in response to the average obtained, one of the maps is selected. A gear shifting is controlled based on the selected map. A driver's intention to decelerate is estimated and is compared with a reference value which increases with increasing said average indicative of the grade of hill that the vehicle is descending. As a result, downshifting will not occur until the driver's deceleration intention becomes great at steep hill descending.