A reliability approach applied to wood structures under seismic excitation is proposed in this paper. This approach is based on First Order Reliability Method (FORM). The mechanical, model which represents a timber roof truss used in individual housing, is detailed and the mechanical nonlinear behavior of the timber joints is defined by hysteresis elements. The uncertainties are taken into account in the numerical model through random variables representing the stiffness parameters at timber joints. The reliability analysis allows us to compute the failure probability and their sensitivity to various random parameters. Numerical examples show the performance and the efficiency of the proposed method.