Abstract: Dynamic changes of root morphology affected by nitrate levels in different maize inbred lines (“478”、“CA170”)are studied in this paper．The results show that increasing the nitrate application level can enhance the shoot biomass as the planting time passes ．whereas “478”is higher than “CA170”at two nitrate concentrations．Compared with “CA170”，the variety of“478”has a longer total root length，average root length and density of laterals to obtain more nitrogen at N deficiency，but this tendency is not so significant at the very beginning of the sampling time(7d)．At high nitrate supply，the density of laterals increases for the two varieties，root average length however，becomes short，and the genotypic difference of the two varieties does not exist．Therefore，A larger root system of“478”is useful to extract much more N especially at low N condition．