This paper deals with the effect of the structure of crustal quality factor Q on the measurement of Q value.Most of reported results show that there is some positive correlation between Q value and ray path of seismic waves.Therefore,for explaining the spatial distribution of observed Q values,not only the effect of seismic frequencies,but also analysing and correcting the effect of ray path on epicentral distance must be considered.Finally,according to current crustal velocity model of Chinese Continent,by calculating the seismic ray path in horizontal layered medium,the authors obtained the functional relation between the epicentral distance and the maximum depth of ray path,and give the structures of crustal Q in North China and partial areas of Southwest China.