>Based on empirical survey data in three Chinese cities，this article intended to find the factors that influenced the economic status attainment of the rural-urban migrant workers in Chinese cities. We found that the human capital of these migrants played an important role in their economic status attainment，while their social capital，i.e.，the accessible resources embedded in their personal social network，showed even greater effect. We also found that the training course that the migrants took in the cities was almost as important to them as their formal school education，which indicated that they have to “transform” their original human capital so as to make it work better in the new environment. Further analysis on the effect of the migrants’ social capital showed that they also have to break the boundary of their “original social capital” built up in the rural world，and to start accumulating their “new social capital” in the cities. These are indispensable steps to ensure their “success” in the new urban world.