The differentiability of the initial stresses and elastic constants of the surrounding rocks of tunnels is discussed firstly from the point of view of finite element method. An interval back analysis model is put forward to identify these parameters based on the measured data of deformation and induced stress in the surrounding rocks. The uncertain property of the measured data is considered and the interval analysis method to solve the uncertain problems is induced in the present model. The interval of the initial stresses and elastic modulus can be obtained by using the constrained variable metric method for the present model.