Abstract: The SPAD-502 chlorophyll meter appears promising for rapid,on-farm analysis of crop nitrogen status.The feasibility of readings of SPAD-502 on the nitrogen nutritional diagnosis of corn was studied through a simple field experiment and research method under field condition.The results indicated that the optimal place for N nutritional diagnosis was middle position of the last opened corn leaf at V9-10 growth stage.There were significant relationships among the readings of SPAD-502 with total N in corn,N application rate as well as corn grain yields.Because different corn varieties influenced greatly on the readings of chlorophyll meter,the readings should be calibrated using comparative chlorophyll meter readings.The prediction accuracy on nitrogen nutrition status using chlorophyll meter after calibration was 66.7% for summer corn.