The low effectiveness of nitrogen (N) from fertilizer is a substantial concern in worldwide which has been threatening the sustainability of sugarcane production. The increment of nitrogen use efficiency (NUE) by sugarcane genotypes associated to the best practices of fertilizer management and nutritional diagnosis methods have higher potential to reduce environment impacts of nitrogen fertilization. Due to the difficult to determine N status in soil test as well as there is not crop parameters to recommend N for sugarcane in Brazil, emerging the possibility to use optical sensor to monitor crop nutritional demand, such as those used to measure indirectly chlorophyll content as N status indicator. This technique is very common for scientific purposes, but for commercial fields it has few adoption. Otherwise, precision agriculture techniques may be one of main alternatives to increase sustainability and crop production, and for localized management of fertilizers, mainly N-fertilizers, which will contribute to save N-fertilizer rate as well as decreasing environmental impacts. Therein it is evident that the application of N-fertilizer for sugarcane might not only be associated to the expected yield, whereas other research go to solve the diagnosis of N status in the soil and the consequent recommendation of N fertilization, the diagnosis of nutritional status of N in sugarcane made by optical sensors "on-the -go" (real-time reading) seems to be one of the promising options to overcome this technological bottleneck. The aim of this work was to assess the nutritional diagnosis of sugarcane crop in N using active optical sensor, performing evaluation throughout the growth cycle of the crop (60 days after the harvest – DAH, 90DAH, 120 DAH, and 180DAH). For this two experiments were established in sugarcane ratoon (2^nd ratoon) of RB95-5970 variety, which has been harvesting mechanically (green harvest system). These fields are located to Tabapuã County, São Paulo State, Brazil. In both areas the same experimental block design was carried out with five treatments (N rates: 0, 50, 100, 150 and 200 kg ha^-1 using ammonium calcium nitrate). The fertilizers was applied 30 DAH in both sides of sugarcane row. During the crop evaluation were done measurements of nutritional status of N by collecting of  leaves (L+1) for N content determination in Laboratory, at the same leaves the chlorophyll content was measured using a SPAD-502 sensor (Spectrum Technologies, Inc, Plainfield, IL), and to estimate vegetative index (NDVI: normalized differences vegetation index  and NDRE: normalized differences redged) an optical active sensor Cropcycle (SOAT - ACS – 430, Crop Circle Holland Scientific, Lincon, NE, EUA) was used. At the end of crop cycle (360DAH) was performed the final harvest to determine crop production (tons of stalks per ha). All measurements performed during the crop cycle were submitted to person correlation. The N-fertilization has increased crop yield in just one of experiments, where the maximum stalks yield was obtained to 100 kg ha^-1 of N. In this experimental area the Pearson correlation showed that NDVI data obtained to 90DAH by the optical active sensor was able to predict 89% of sugarcane yield (y=-4888.5x² + 5779x – 1614 R²=0.89). The N content in leaves (L+1) has correction to N rates during 120DAH (R²=0.62), and in this date the both optical sensor was able to predict the differences among treatments having correction to N content in leaves (R²=0.50 for SPAD and R²=0.49 for Cropcycle). The results from this work showed an interesting possibility of N predict demand, which has been encourage our group to evaluating more areas focusing to obtain a mathematical model to predict N demand by sugarcane through Cropcycle sensor measurements, and then creating a way to apply variable rate of N fertilizer in commercial sugarcane fields.