In this paper, a separation model for blunt dissection simulation of a brain surgery is discussed. In the separation model, fracture behavior of brain tissue and its representation in the simulation are important. A brain tissue is modeled by using finite element method. The finite element model is composed of three layers in which a connective tissue model is sandwiched between two brain parenchyma models. In order to represent the fracture behavior in the finite element model, when the principal stress generated at an element exceeds its maximum, the element is removed from the model. In order to validate the separation model, fracture experiments are performed using a agar. The experimental results are compared with the fracture simulation results.