-

Literature review of business cycle in economic studies is very old. The economist's viewpoints are focused on two directions. Recognition of effective factors, and statistical characteristics of business cycle.
In this paper, the business cycle of Iran's economy is investigated for 1959-200 I. The methodology consists of four steps: the firs, to estimate the long-run trend of real GDP in linear form, the second, to measure deviation of real GDP from long-run trend, this gaps means, there are periods of recession and boom in economy, the third, to investigate that, the gaps of GDP are stochastic or there is a serial correlation model, we answered this question by Run-Test method. And the fourth, if serial correlation model is confirm how many years length of time a period of business cycle in Iran economics? We estimate by Box-Piers statistic.
As a result: There are serial corelations in business cycle of Iran and the period of one cycle is a bout 11 years. In addition: oil incomes, investment, budget deficit and liquidity are the most important factors in forming business cycle ofIran's economy.
Long-run Economic policies for modified business cycles by this paper are obvious.