As the gap in income between urban and rural residents bigger and bigger, based on the data from 1978 to 2007, this paper makes an empirical study of the dynamic relation between the fixed assets investment and the difference in income between urban and rural residents. The outcome from the study indicates a long-term balance exists between the investment rate of the fixed assets and the difference in income between urban and rural residents. A short-term deviation from the balance can be adjusted through long time. To a certain extent, city-oriented fixed assets investment policy is the main cause of the big gap in income between urban and rural residents. The big gap in income between urban and rural residents in turn reinforces their social status, thus further strengthening the city-oriented instead of countryside-oriented fixed assets investment policy. Based on that, this paper puts forward some suggestions on adjusting the fixed assets investment policy so as to shorten the difference in income between urban and rural residents and realize the goal of harmonious development between city and countryside.