We take cross - sectional data on manufacturing industries from 34 major cities of China in 2003 for analysis, in order to reveal the influence of agglomeration on manufactory productivity, The results verify that agglomeration really accounts for the discrepancy of productivity among the big cities, and the influence of localization economies is more prominent than that of urbanization economies. In addition, the impact of agglomeration on productivity varies among different sectors of manufactory industries and among west, middle and east China as well.