Retrieving the vertical distribution of aerosol mass concentration by detecting the vertical distribution of extinction coefficient with lidar is important in environment monitoring. It is indispensable to establish the relationship between extinction coefficient and mass concentration. The relation of mass extinction coefficient, extinction coefficient and mass concentration is analyzed based on the Mie scattering theory, an equivalent parameter is introduced and the effect of Junge index on the equivalent parameter is discussed. The relationship between aerosd extinction coefficient and mass concentration is validated by measured particles spectrum distribution, visibility, relative humidity and aerosol mass concentration in Beijing,which is significantive for retrieving aerosol mass concentration with lidar.