With the rapid development of the economy, the role of the tertiary industry’s output becomes more and more important to the development of economy. With ARIMA modeling, this paper forecasts the output of the tertiary industry of Chongqing, based on the 2013 Chongqing statistical yearbook. The results implies that ARIMA(1,2,2) provides the accurate result and has good fitting degree, so it can be used to predict the future. Therefore, it can provide reliable theoretical support for the prediction for the output of the tertiary industry of Chongqing.