An approach has been developed to identify the position of voids in structures using topological derivative and level set method. The position of voids is identified by solving an optimization problem. The level set method is applied in the present approach to represent the voids. The topology derivative of the objective function is used to produce voids in the problem domain. The shape derivative of the objective function is used to evolve the boundary of the voids. This approach has been applied to the voids identification of two-dimensional (2D) structures, the examples with multiple voids are considered. The results indicate that the voids in structure can be identified effectively by the present algorithm.