With Kenjian 5 Rice as experimental materials, the effects of water supply during the stage of before-head-ing on filling dynamics and yield of rice in cold regions were studied with pots under rainproof shelter. Water dynam-ics in the pots were monitored by examining soil water potential(SWP) using negative pressure soil moisture tensi-ometers. The results indicate that intermittent irrigation at SWP between -8~-10 kPa increased economic yield of Kenjian 5 Rice significantly, along with increases of average growth rate(G) and maximum growth rate(Gmax) of the superior grains and inferior grains and decreases of G and Gmax of the middle grains. The in-dex I values of superior grains and middle grains were improved, despite those of the middle grains. The growing active days(D) were shortened for the superior grains, while elongated for the inferior grains and middle grains. The weight per 1 000 grains(W-~axa) was increased for all the three grades of the rice grains. On the contrary, with unremitting irrigation at SWP between -18~-20 kPa and-28~-30 kPa during the stage of before-heading, economic yield of Kenjiandao 5 were significantly reduced, indicating by increased and Gmax values for the superior grains and decreased G and Gmax values for the middle grains and inferior grains, and raised I values, shortened D and increased W a for the grains of all the three grades.