Abstract: A driving force acceleration calculation method is executed by a processing module; the driving force acceleration calculation method includes receiving a tilt sensing signal from the tilt sensing unit, a sensed angle and a sensed acceleration from the gravity sensing unit; determining whether the tilt sensing signal is an uphill signal or a downhill signal; when determining that the tilt sensing signal is the uphill signal, calculating a driving force acceleration as the sensed acceleration plus the gravitational acceleration component; when determining that the tilt sensing signal is the downhill signal, calculating the driving force acceleration as the sensed acceleration minus the gravitational acceleration component; outputting the driving force acceleration; the method is able to more accurately calculate the driving force acceleration of a bike, therefore better knowing whether the bike suddenly decelerates.