Numerical calculation of structural failure probability is one of an important approach to predict structure remained service life. A novel method was developed to calculate the failure probability of spatial truss structure based on the theory of three-order coupling failure of a structural system. In this method, the stress change rate method and element-removing method were combined to evaluate correlation coefficient of failure modes of the bar. The coupling probability method was applied to analyze the expression of the upper and lower bounds of structural function under different failure modes, and it was verified and compared with the Taylor expansion method. Besides, damage test of a six star-type dome was conducted. By which, the time history of stress of bar was recorded during the process by a stress rate method, and the variation characteristics of six star-type dome failure and structural failure probability intervals were concluded. The results show that the coupling probability method can well show the combined failure results among multiple subsystems. The method of converting multi-dimensional integrals into one-dimensional integrals has high calculation accuracy and good applicability. It can be used effectively to analyze the failure profanity of spatial truss structure and predict structure failure mode and analyze structural characteristics in numerical.