We present a preliminary investigation on the spectroscopic properties of geostationary earth orbit satellites (GEO). The optical wide-field net system (OWL-Net) has been developed and used for tracking and monitoring of low earth orbit satellites (LEO) and Korean GEOs since 2010, and complementary spectroscopic data for four GEOs were acquired using the 1.8 m telescope at the Bohyunsan Optical Astronomy Observatory (BOAO). Reflectance spectroscopy of GEOs is a useful technique to investigate the surface material and their attitude. Furthermore, long term spectroscopic observations covering time variations will provide comprehensive data on the space weathering effects in the GEO orbit environment. Previous spectroscopic analysis of a meteorological GEO COMS has revealed interesting emission features including H-alpha and sodium lines. Subsequent follow-up spectroscopic observations on the GEOs (KOREASAT-5, -6, and COMS) using Longslit spectrograph at the BOAO are scheduled throughout 2018 for a further study of GEO orbit environment.