This experiment was focused on the effect of organic fertilizer and planting density(60,75 and 90 thousand plants/hm²) on root growth and function of maize in field condition.The result showed that basal organic fertilizer reduced root length and surface area in 30-100 cm soil layer at pre-tasselling stage,but had no significant influence on root dry weight.The rate of root/shoot was significantly decreased because organic fertilizer dramatically increased the biomass of shoot.The influence of planting density on root growth was not significant.At waxen maturity stage,basal organic fertilizer restricted the distribution of root in 30-100 cm soil layer and at the position of 1/4 row space,1/2 row space,under plastic mulch,but had no significant influence on root/shoot.The trends of root length,root surface area and root dry weight were decreased as planting density increasing,especially in 0-30 cm soil layer and at planting position.The increase of planting density also decreased the rate of root/shoot,but increased the root function.Organic fertilizer also didn't show the significant effect on deferring senescence and had no significant difference in hydraulic conductivity of root system compared with the treatments without basal organic fertilizer.Root showed some flexibility by increasing water uptake function per surface area as planting density increasing.