Concrete tensile stress-strain curve is one of the basic mechanical properties of the material. To gain complete stress-strain curve of axial tension need complete test conditions, this article provided a simple test device to measure concrete direct tensile stress-strain curve. Due to the shortage of the descenting stage data in testing process,GM(1,1) model was established to forecast descenting stage on the basis of the gray system theory, which provide a simple menthod to gain the descenting stage of direct tensile at engineering site to convenient for analysis of the whole stressing process of concrete structure.