Portable active remote sensing spectrometer-Greenseeker and chlorophyll meter (SPAD 502) were used to determine NDVI and SPAD meter readings of corn at different growth stages under different nitrogen levels. This paper studied the impact of nitrogen on the nutritional status of single plant and corn population, and simple, fast and non-destructive nutritional diagnosis methods of crop nitrogen status in the field. The research results showed that NDVI increased with N rate, reaching a plateau at N 300 kg/hm^2. The relationship between NDVI and nitrogen rate could be described with a linear plus plateau model. Corn NDVT changed with different growth stages: NDVI was at a low level at the seeding stage and increased to the highest level at the pre-tasselling stage, then declined gradually and stabilized after tassel stage. The changes of NDVI and SPAD values showed similar trend. SPAD readings and chlorophyll contents were positively correlated, and SPAD readings at pre-tasselling stage were positively correlated with grain yield. This paper proved that portable active remote sensing spectrometer-Greenseeker and chlorophyll meter (SPAD meter) could be integrated to diagnose corn nitrogen nutritional status.