Crop canopy sensor-based in-season site-specific nitrogen (N) management is a promising approach to precision N management. GreenSeeker sensor has previously been evaluated in North China Plain (NCP) for improving winter wheat N management, and it was found that NDVI became saturated when winter wheat biomass reached about 3700 kg ha^-1. A new active canopy sensor, Crop Circle ACS-470, has 6 wavebands, and has the potential to improve the estimation of crop N status. The objective of this research was to compare these two sensors for estimating winter wheat N status at different growth stages. Five field experiments were conducted in Quzhou Experiment Station of China Agricultural University in 2010 and 2011. Preliminary analyses indicated that both sensors performed well for estimating winter wheat biomass and N uptake, but several vegetation indices calculated with Crop Circle ACS-470 sensor performed significantly better than GreenSeeker NDVI and RVI for estimating plant N concentration. The Crop Circle sensor has a better potential for in-season site-specific N application in North China Plain, and more researches are needed to develop algorithms for making in-season N recommendations.