Despite wide usage in reinforced soil projects, geotextile is featured with big challenge and low precision in strain measurement as it is a flexible material of low elastic modulus. The role of geotextile in engineering as well as the strain of geotextile are still uncertain. In this article, we proposed a method of accurately measuring the strain of geotextile by controlling the shape and thickness of a flexible binder to paste strain gauges, which, hence deforming in coordination with geotextile. Moreover, we also developed an equipment for calibrating the stress-strain of geotextile, by which the observed value of strain gauge can be transformed to the actual deformation of geotextile. The equipment’s applicability was verified by centrifugal model test. The research achievement offers technical support for further researches on geotextile’s reinforce mechanism and influence on mold bag sand cofferdam stability.