Abstract: Based on the experiment, the tensile strain-stress relationshipwas set up by means of the stochastic theory. Researches proved that the complete curve for concrete under tension was caused by the gradually fracturing of bond and cementitions colloids during loading. It was also proved that the method proposed in this paper can be applied not only to explain many test results and to determine the tensile complete curve for concrete under tension, but also to obtain some results which are difficult to get from test.