In a concentration solar system, large temperature differences occur between the hot- and cold-junction of thermoelectric module due to concentration technology. Therefore, the nonlinear temperature dependence of the Seebeck coefficient, the electric conductivity, and the thermal conductivity of thermoelectric materials should not be neglected in performance evaluation of thermoelectric generator. Herein, a discrete numerical model, with advantage of low-computational expense, high accuracy, and broad application scope, is built to design the thermoelectric generator in a concentration solar system. Temperature-dependent material properties and contact resistance are both incorporated in the discrete numerical model. Besides, an experiment is carried out to measure the performance of Bi₂Te₃ thermoelectric generator operating under various temperature differences (T). Finally, the discrete numerical model-calculated results are compared to the experimental data and the theoretical results computed by the commonly used constant properties model. Results show that the variation between the constant properties model-calculated output power and the measured one is less than 4% with T lower than 59 K and rises to 12.6% with T up to 251 K, while the error between the discrete numerical model-calculated output power and experiment remains lower than 2% even when T is above 251 K.