This paper uses the ARMA model method to fit the data of the urban and the rural residents’ per capita income in China and builds the MA(2) and AR(2) model. With the model, this paper predicts their trends in 5 years, also uses the prediction to analyze the income gap. The results show that in the next 5 years, the rural and the urban residents’ per capita income will be increasing steadily, but the level remains very low, the income gap is still large.