Optical Spectroscopy, as a powerful and applicable Non-destructive Testing (NDT) technology, is capable of solving many problems in agriculture based on quality, safety and health assessment of the sample (plant or crop, food, soil, water, etc.). This non-destructive optical technology can be used for development of smart spectral sensors and systems, the most important objects that can be connected to the Internet with the potential to collect, store, process and analyze the spectral data and information, and control or communicate remotely. Recent advances in non-destructive Spectroscopy technology in combination with emerging and advanced technologies such as Internet of Things (IoT), Big Data, Cloud Computing, and Artificial Intelligence technologies, play an important role in developing Smart Agriculture and improving the agricultural productivity. This article aims to present the role of this Non-destructive Testing technology in the future of Smart Agriculture by introducing its most important applications in solving key challenges facing agriculture based on sample quality, safety and health assessment.