This thesis presents a spectral analysis of the high-mass X-ray binary system Vela X- 1 using archival data from the Neutron Star Interior Composition Explorer (NICER). Vela X-1, a well-known eclipsing system consisting of a neutron star and a supergiant companion, serves as a standard for studying wind-accreting high-mass X-ray binaries (HMXBs). By applying phase-resolved spectroscopy across eight NICER observations, we explore the variability of key spectral parameters, particularly the hydrogen column density nH and cutoff energy Ecutoff, as a function of orbital phase. Spectral fitting was performed using various models, with the most comprehensive model tbabs*(bbody+cutoffpl) resulting in the best fit across most observations. The inclusion of a Gaussian emission line component significantly improved fit quality, suggesting the presence of features such as Fe kα fluorescence. Observed variations in nH are consistent with the neutron star passing through regions of the stellar wind, while pronounced absorption near eclipse phases suggests obscuration effects due to the companion star. These results reinforce the importance of orbital phase in understanding the accretion dynamics and spectral characteristics of wind-fed X-ray binaries.