The figure of merit of thermoelectric materials is temperature dependent, and thus the local compatibility factor changes significantly along the thermo-element length. A local optimization method to maximize the efficiency of a function graded thermoelectric generator was proposed and discussed in this paper. By adjusting the cross-sectional area and segment's thickness, the reduced current equaled the compatibility factor of the material at every local thermo-element layer. This method can use the full potential of existing materials by maximizing the efficiency at every local thermo-element segment. For such a TEG working in a temperature range of 300-1100 K, the efficiencies of P-type segmented Bi0.5Sb1.5Te3/BiSbTe/-PbTe/FeNbSb thermo-element and a N-type segmented Bi2Te2.79Se0.21/Bi2Te2.9Se1.1/SnSe/SiGe thermo-element were 25.70% and 21.73%, respectively, much higher than the conventional segmented thermo-elements. The overall efficiency of the device was more than 23.72%, making it a promising technology to harvest energy from medium and high-temperature industrial components. The optimized TEG can be fabricated by SLS/SLM technology. Published by Elsevier Ltd.