Abstract: In assembling an automobile, the cable of handbrake mustbe pre-tightened appropriately. The tension is usually measured andcontrolled by a technique called ``the tri-point method''. However, theresults obtained do not agree with the actual ones.Generally, people ascribe this discrepancy to bending rigidity of the cable.This paper presents a new calculating model without bending rigidity bymeans of considering the actual force condition of a cable. Calculatedresults agree with the actual ones properly and therefore the technical problem of quicklymeasuring the tension of cables is resolved theoretically.