Thermoelectric generator offers many advantages such as high durability, environmental protection, and high reliability. Since the geometric optimization of a thermoelectric generator is a proper way to improve the performance, this study considers the multiparameter optimization of thermoelectric generators to investigate the effect of cross-sectional area ratios and contact resistance on the performance of thermoelectric generator. Here, a x220f;-type cascaded thermoelectric system with two stages including two p-legs and two n-legs is examined numerically by ANSYS Workbench. The effectiveness and efficiency are obtained for different electric contact resistances. The results show that with a decreasing of the electric contact resistance, the efficiency and effectiveness are increased. Also, higher output power and efficiency of the TEG device are observed with a suitable ratio of cross-sectional area.