Sm0.3Ce(0.7-x)MoxO(1.85+δ) yellow pigments were prepared by solid-state synthesis method, which were obtained by doping molybdenum for substitution of Ce4+ in Sm0.3Ce0.7O1.85. Effects of Molybdenum doping amount on crystal structure of the pigments were investigated and the coloring mechanism of the pigments was analyzed. The results show that molybdenum doping has markedly changed the color of the pigments. The color of pigments changed from cream to yellow as molybdenum doping amount increased from x=0.00 to x=0.04. And the color changed from yellow to yellow green when x was adjusted from x=0.05 to x=0.07. When x=0.08, the color of pigments changed to gray.