For the purpose of investigating the diffusion behavior of chromium, nickel, and molybdenum into iron during the sintering of iron powder, metallic cementation was carried out concurrently with the sintering by heating the pre-compressed iron powder which had been embedded in chromium, nickel, or molybdenum powder. A microscope and an X-ray probe microanalyzer were used to observe and analyze the diffusion layer. The results showed that the depth of diffusion layer increased with the rise in sintering temperature or with the decrease in pre-compressed pressure on the powder, and the thickness of diffused layer increased linearly with the increase of treating time. The results of additional tests showed that chromium and nickel were simultaneously diffused into iron when the pre-compressed iron powder was embedded in a mixed powder containing chromium and nickel at a proper ratio. The diffusion coefficient of chromium was evaluated in the process of simultaneous sintering and metallic cementation.