A general mathematical model of the AMTEC/TEG hybrid system consisting of alkali metal thermal electric converter (AMTEC) and thermoelectric generator (TEG) has been developed, in which the load parameters and main geometric parameters were considered. Instead of specifying some parameters, the evaporating temperature and condensing temperature of the AMTEC as well as the operating temperature of the TEG subsystem were determined by solving energy balance equations. Restilts show that electrode current density has a quite noticeable influence on both AMTEC subsystem and TEG subsystem. The maximum conversion efficiencies for AMTEC and AMTEC/TEG are 27.42% and 31.33%, respectively. Besides, it is interesting to note that the optimal value of the ratio of thermoelectric module area to electrode area is always near 0.2 regardless of the ratio of evaporator heat transfer area to electrode area. The length of thermoelectric arms 1 and the ratio of the thermoelectric couple area to the total area of the thermoelectric module b are critical factors, b >= 0.55 and l <= 11 mm should be satisfied to obtain a compact and low-cost system.