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A field experiment was carried out to study the effects of different water and phosphorus managements on dry matter accumulation, phosphorus uptake and utilization, yield of rice at the maturity stage in cold black soil region, the relationship between root traits and phosphorus uptake efficiency at heading stage was discussed. Two irrigation modes (F: flood irrigation, C: controlled irrigation) and six phosphorus application levels (P0:0kg/hm2,P1:15kg/hm2,P2:30kg/hm2,P3:45kg/hm2,P4:60kg/hm2,P5:75kg/hm2) were set, the effect of different water and phosphorus managements on aboveground dry matter, yield and its components, phosphorus accumulation in grains and plants, phosphorus use efficiency, phosphorus uptake efficiency and phosphorus fertilizer partial productivity were studied. The results showed that under two irrigation modes, with the increase of phosphorus application rates, the aboveground dry matter, yield, effective panicle number, seed setting percentage, phosphorus accumulation in grains and plants were increased firstly and then decreased, and harvest index, phosphorus harvest index, phosphorus use efficiency of grain and dry matter were decreased firstly and then increased, however, the phosphorus uptake efficiency and phosphorus fertilizer partial productivity were decreased. The aboveground dry matter, yield, effective panicle number, seed setting percentage, phosphorus accumulation in grains and plants of CP2 and FP3 reached the maximum, respectively, among the different water and phosphorus treatments. There was no significant difference in yield between CP2 and FP3 (P>0.05), however, the phosphorus fertilizer partial productivity of CP2 was significantly higher than that of FP3(P<0.05). Therefore, CP2 treatment was the best water and phosphorus management in this experiment. The correlation analysis showed that there was a positive correlation between yield and aboveground dry matter (P<0.01) and a significant negative correlation between yield and harvest index (P<0.05). Plant phosphorus accumulation was positively correlated with aboveground dry matter (P<0.01). Plant phosphorus accumulation was positively correlated with root dry weight and root length density (P<0.05). The results indicated that suitable water and phosphorus management could create good root morphology, increase dry matter accumulation, which was more conducive to improving yield and phosphorus use efficiency. The research results provided theoretical basis for understanding the difference of rice root morphology and phosphorus fertilizer utilization under different water and phosphorus managements and guiding the practice of high yield and high efficiency cultivation of rice in cold black soil region. 