The invention discloses a phosphoric acid fuel cell and two-stage semiconductor composite power generation device. The device comprises a PAFC device and a TTEG device, and the device is characterizedin that the PAFC device comprises PAFC, wherein a cathode and an anode of the PAFC device are porous graphite electrodes coated with platinum catalyst mixtures, and an electrolyte of the PAFC deviceis a phosphoric acid solution dispersed in a silicon carbide substrate; the PAFC converts chemical energy in fuel into electric energy through electrochemical reaction, outputs the electric energy, and generates waste heat; the TTEG device comprises a top-layer thermoelectric semiconductor, wherein the waste heat generated by the reaction of the PAFC is used as a high-temperature heat source, andthe electric energy is generated under the action of temperature difference; a bottom thermoelectric semiconductor generates electric energy under the action of temperature difference by taking heat released by the top thermoelectric semiconductor as a high-temperature heat source and taking the environment as a low-temperature heat source. According to the method, the TEG is used for recovering the PAFC waste heat to generate extra electric energy, the PAFC waste heat is reasonably recovered, and the stepped utilization of energy is achieved.