High-mass stars are very important to many areas of Astronomy. These objects deeply impact their surroundings through their powerful winds and their deaths as supernovae. Therefore,understanding the behavior of such stars is essential to understand their impacts on their hostgalaxies' properties and history.The aim of this research project is to analyze the atmospheres of B supergiants (BSGs, evolvedmassive stars) using the CMFGEN (Hillier & Miller 1998), a 1D, non-LTE atmosphere code — which is one of the state-of-the art tools used to analyze hot stars. The focus of the project is to investigate whether more recent models (e.g., the inclusion of x-rays, clumping, more recent atomic data) can better explain the optical and UV observed spectra of these stars, since previous studies failed to model several important UV lines (Crowther et al. 2006; Searle et al. 2008).As results we obtained (i) an overall improved agreement between BSGs observed and model spectra at the UV considering the effects of clumping and x-rays in the wind. Also we noticed (ii)important differences in their properties between hot (B1 – B0) and warm (B2 - B5) BSGs were also found, and it is in agreement with recent hydrodynamical simulations, such as Driessen et al.(2019). Beyond that, (iii), we have found a general trend of the CNO abundances for BSGs compatible with previous works in the literature and to the current high-mass stellar evolutionpredictions. However, (iv) despite a decrease in terminal velocity at the Bi-Stability Jump, we found no increase in mass-loss, instead, we have found a slightly decreasing trend towards later spectral types.