Abstract: A stiffness derivative technique to deter min e the strain energy release rate has been generalized to the plane strain fracture problem of piezoelectric materials. By using the numerical solution to piezoelectric materials obtained by finite element method as the actual fields and Sosa's asymptotic expressions for the electricmechanical fields in the vicinity of the crack as the auxillary fields, the generalized reciprocal M integeral method is used to solve the stress intensity factors K I ,K ...