Abstract: To support design and evaluate the performance of vapor-fed alkali metal thermal to electric conveter (AMTEC) cells, based on pressure model, electric model and thermal model of vapor-fed AMTEC, the analysis approach for thermoelectric conversion performance of AMTEC was developed. The validation was performed through studying electrical power output, thermoelectric conversion efficiency and load following performance of AMTEC module in SAIRS-C. The predictions of power output and thermoelectric conversion efficiency obtained by the approach show general agreement with the reference data, but there is deviation between calculation value of load following and reference value. This approach is capable to apply to analyzing and evaluating the performance of vapor-fed AMTEC cells, and it needs further improvement when used in the cell design.