Shearography, a type of speckle interferometry, is a powerful tool for nondestructive testing (NDT) because it is insensitive to environmental vibration disturbance and easy to detect strain concentration in an internal defect with noncontact and whole field. The shearing amount in Shearography has influence on determining defect size and source location. Thus the shearing amount must be optimally adjusted to get accurate evaluation. This paper investigates the defect size and source location according to the change of shearing amount in artificial slender defects along longitudinal direction of pipeline. Based on the investigation, a new technique is proposed for the quantitative determination of defect size and source location.