In timber elements the mixed mode depends essentially of wood anatomy and load configuration.In these conditions, in order to evaluate the material behavior and the fracture process, it’s necessary to separate the part of each mode. The mixed mode separation allows evaluating the amplitude of fracture mode. In the present paper, using a mixedmode crack growth specimen made in Douglas fir, the mixed mode crack growth process is study thanks to marks tracking method. Using the marks tracking method the characteristic displacements associated to opening and shear mode are measured. From the experimental measurements, the energy release rate associated to opening and shear modes is calculated into to account the crack advancement during the test.