Abstract: The thermal mismatch phenomenon in thermoelectric generator(TEG) arrays can lead to device damage and seriously affect the efficiency and reliability of the generation units. In order to analyze the electrical characteristics of TEGs and the effects of thermal mismatch on the arrays, an analytical method is proposed to analyze the electrical characteristics of TEGs through the analysis of Kirchhoff’s voltage and current law; meanwhile, an experimental platform for TEGs with low-grade heat source is built, and the experiments and analysis of thermal mismatch are carried out based on the built TEG platform. The maximum output power of each array is measured, and the loss rate of each array is calculated to quantify the effect of thermal mismatch on temperature difference power generation. Finally, it is found that the temperature mismatch causes a significant decrease in array power, the series-parallel(SP) structure has higher efficiency than the rest of the arrays, the uniformity of temperature distribution has a strong correlation with the output power of temperature differential power generation, and the complexity of the array connection has a correlation with the output power of temperature differential power generation.