According to the piezoelectric material damage theory and the fracture criterion based on damage theory, which has been established by Yang et al, reliability analysis of a damaged piezoelectric truss is carried out. The expression of safety margins of the piezoelectric beam has been proposed, with the mechanical damage extension force, electric damage extension force, Inertia Moment of cross-section and nodal loads as stochastic variables. Then the truss is dealt with randomly, and the corresponding reliability index is got according to the Taylor stochastic finite element. The result indicates that the reliability of the system is influenced greatly when the positive and negative electric fields have been applied on the structure, which provides the basis to control the reliability of structural system. Finally, through a calculation example, the quantification results of the reliability index are compared under the conditions of positive electric field, negative electric field or no electric field.