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In order to suggest an efficient catalyst system for automotive emission control, Pd-WO3 and Pd-La2O3 catalysts were characterized before and after simulated thermal aging and phosphorous contact. From the results of H2 chemisorption experiment, it was found that the particle size of Pd was decreased and the dispersion of metal was increased by the promotion of La2O3, which results in the enhancement of thermal durability. Also it was found that deactivation of Pd-WO3 involves severe metal vaporization during thermal aging. By engine exhaust gas test, it was observed that Pd-La2O3 catalyst was sensitive against phosphorous poisoning up to certain value of phosphorous accumulation while it has exceptional thermal stability.