A T-S curve correction method for a clutch system may include: detecting differences between actual positions of a clutch in first and second torque regions and a position on a T-S curve; determining whether the difference between the actual position in the first torque region and the position on the T-S curve is equal to or more than a first reference value; determining whether the difference between the actual position in the second torque region and the position on the T-S curve is equal to or less than a third reference value, when the difference of the actual position in the first torque region is equal to or more than the first reference value; and correcting the slope of the T-S curve in the increasing direction, when the difference of the actual position in the second torque region is equal to or less than the third reference value.