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• A three-dimensional numerical model based on the finite element method has been developed. • A multi-factor roadmap for the design of wearable micro-TEGs is proposed. • A micro-TEG module is fabricated to verify the theoretical roadmap. • The maximum power density reached 1.79 μW/cm2 for the micro-TEG module worn on the wrist. To further meet the requirement of the Internet of Things (IoT), more and more sensors need to be integrated inside wearable devices. Wearable TEGs directly convert the heat flow generated by the temperature difference between a human body and the environment into electricity, thus acting as a permanent energy supply for sensor systems. In this work, considering the body's thermoregulation function in the wearing scenario, a three-dimensional numerical model based on the finite element method has been developed to systematically study the power generation performance of micro-TEGs. The multi-factor design involves the packing density (p d), leg width (w), leg height (l) and convective heat transfer coefficient (h) at the cold side of the generator. On this basis, we have proposed a multi-factor roadmap for the design of wearable micro-TEGs with the required power density and open circuit voltage. The theoretical roadmap modeling was verified by fabricating a micro-TEG module of 20 × 20 mm2, with w = 0.5 mm, l = 1.38 mm, and the leg density of p d = 33 legs/cm2. When worn on the wrist (T core = 37 ℃, T air = 22 ℃), a steady voltage output of ∼ 21.0 mV was generated and the corresponding maximum power density reached 1.79 μW/cm2. [ABSTRACT FROM AUTHOR]