Since 1978, China has enjoyed rapid economic growth and become the world second economy but subprime crisis not only brought great effect to the economy of the world but to China's economy as well. Though China's economy showed a brief growth resumption through a strong stimulus, a gradual decline appeared soon afterwards. In 2014, China's GDP growth rate was 7.4%, compared with the rapid growth before the economic crisis, there is a big gap. With the application of the seasonal adjustment model and Hodrick-Prescott filter analysis, the paper finds that China's long-term economic growth rate has a downward trend. This paper further argues that the basic factors of China's downward economic growth rate is the declined driving force in consumption, investment and net exports and the direct factor is the descending real estate industry. To maintain long-term and stable growth of economy, the paper suggests that China should encourage population growth, lower taxes and technological innovation.