In order to investigate the production mechanism of oil flax under different coordination with water-nitrogenous fertilizer,we used ‘Longyaza 1’ to as material to elucidate the effects of nitrogen and irrigation interaction on dry matter accumulation,distribution and grain yield of oil flax.The split plot design was employed with main plot of water(W₁,irrigation amount was 60 mm at stem stage;W₂,irrigated at stem and flowering stage,and irrigation amount was 60 mm and 40 mm;W₃,irrigated at stem,squaring and flowering stage,and irrigation amount was 60 mm,40 mm and 40 mm),sub-plot of nitrogen fertilizer(N₁,0 kg·hm^-2;N₂,75.0 kg·hm^-2;N₃,112.5 kg·hm^-2;N₄,150.0 kg·hm^-2).The results showed that:(1)the irrigation amount and N application rate has a significant effect on dry matter accumulation and distribution,and there was extremely significant interactive effect between irrigation and nitrogen rate on grain yield,moreover,irrigation rate played a more important role than nitrogen rate.(2)Compared with other treatments,dry matter distribution in grains at maturity stage and contribution of dry matter accumulation amount after anthesis to grains under the same N application levels were markedly raised and grain yield was significantly increased by 10.51%-27.99% in W₂.(3)The contribution of dry matter accumulation amount after anthesis to grains at N₃ levels under the same irrigation conditionswas significantly increased by 7.90%-42.43%;at the W₂ and W₃ irrigation level,the grain yield of N₃ treatment was the largest,but over-fertilization of nitrogen caused significantly reduction of yield with a drop of 7.96%-9.62%.Therefore,water and nitrogen coordination played a key role in dry matter accumulation and distribution,which was closely related to the grain yield;the nitrogen rate of 112.5 kg·hm^-2,irrigation amount of 60 mm and 40 mm at stem and flowering stage in the whole growth period was optimal combination of irrigation and nitrogen for the higher grain yield of oil flax under the conditions of this experiment.