A basic model of semiconductor thermoelectric generator is constituted. Based on the steady conduction equation, thermodynamic process has been analyzed. Temperature function, output power and generating efficiency of p and n semiconductor are obtained. The Seebeck coefficient S of a kind of Bi-Te-Sb-Se thermoelectric material at low temperature has been experimentally researched. Based on the experiment, the function between S and T of this material has been expressed. The conclusion indicates that this kind of thermoelectric material is unsuitable for power generation at low temperature, and only the enhancement of production technology or appearance of new production method can improve the electrical power generation performance.