This paper analyzes the time series of the traffic flow at Yuquanying freeway of Bejing from No.1 to 10 August 2006 and author finds the multifractal characters.The self-similarity of the time series of the traffic flow are found by using the method of power spectrum and statistical moments.The width,max.and asymmetry parameter of multifractal spectrum are employed in studying the traffic flow time series,which shows the strong degree of multifractality in the time series.This will provide an important theoretic foundation for researching multifractality in the theory of traffic time series.