Electron transport is analysed in Bi2Te3 quantum well of Bi2Te3/PbTe superlattice. The hybrid quantum-classical size effect model, considering the Boltsmann transport equation and classical size effect, is introduced to analyse the effect of rough interface on the electron transport and scattering and the thermoelectric figure of merit of Bi2Te3/PbTe superlattice. The PbTe barrier thickness is kept constant to avoid the influence of the variation in tunnel effect on attenuation of the carrier concentration in Bi2Te3 quantum well of Bi2Te3/PbTe superlattice. The result shows that roughness has strong influence on the thermoelectric figure of merit of Bi2Te3/PbTe superlattice. The Bi2Te3/PbTe thermoelectric figure of merit decreases with the decreasing of the portion (p) of mirror reflection in the hybrid effects. And when p is 0.3, the figure of merit is close to the experiment value.