Scientific irrigation and nitrogen management is important for agricultural production in arid areas. To quantify the effect of water and nitrogen management on yield components, biomass partitioning and harvest index ( ) of maize for seed production with plastic film-mulching, field experiments including different irrigation and N treatments were conducted in arid north-west China in 2013 and 2014. The results indicated that kernel number per plant ( ) was significantly affected by irrigation and N treatments. However, 100-kernel weight was relatively stable. Reducing irrigation quantity significantly increased stem partitioning index ( ) and leaf partitioning index ( ), and decreased ear partitioning index ( ) at harvest, but lowering N rate (from 500 to 100 kg N·hm ) did not significantly reduce , , and at harvest. was significantly reduced by reducing irrigation quantity, but not by reducing N rate. Linear relationships were found between , , , at harvest and and evapotranspiration ( ).