Abstract: Ear traits are most important factors in yield components.In this investigation，six ear traits including ear length(EL), ear diameter(ED),ear row number(ERN),row kernel number (RKN),grain yield per ear(GY) and 100 kernel weight(KW), had been analyzed using a population with 203 F2：3 families derived from an elite maize（Zea mays L.） cultivar Nongda 108（Huang C×Xu 178）， field trials were conducted under nitrogen input (N+) and stress( N-) conditions in Zhengzhou and Xinzheng in 2004, the linkage map including 189 SSR markers covering the 10 chromosomes of maize and the Composite Interval Mapping(CIM) method were used to localize the quantitative trait Loci of ear traits. The results showed that N- stress had more influence to the parent Huang C than to Xu 178. Correlation analysis indicated that EL, ED,ERN and RKN were mainly significant/highly significant positive correlation with GY. Through 1000 times permutation test to have proper LOD threshold values for ear traits, total of 53 QTLs were identified under N+ and N- conditions in two locations. The 28 QTLs detected in Zhengzhou mainly clustered in chromosome 2,8 and 9(occupied by 57.14%),while the 25 QTLs identified in Xinzheng mainly clustered in chromosome 1,2,6,7 and 8 (occupied by 60%). Among the 53 QTLs, 13（24.53%）QTLs appeared to be additive, 20（37.74%）partial dominance , 6（11.32%）dominance and 14（26.42%） over- dominance , the phenotype variation explained by a single QTL varied from 7% to 23%. Only 3 QTLs(qED2a,qKW8a,qKW10a)were both detected under the two nitrogen levels in Zhengzhou，and 1 QTL(qEL1a) both detected in Xinzheng，While only 2 QTLs(qRKN8b,qGY1a) detected at both sites. However，the rest QTLs located in different chromosome or different position on the same chromosome. The QTLs of all traits identified only under low nitrogen stress condition might be relation with nitrogen high use efficiency in maize.

Key words: maize, ear traits, nitrogen use efficiency, quantitative trait loci(QTL), maize, ear traits, nitrogen use efficiency , quantitative trait loci(QTL)