The project of studying the structure of hot stars and the nature of their variability is presented. We propose the three-phase model for hot star winds and calculate the X-Ray line emission of hot component of wind in a comparison with a XMM-Newton X-Ray spectra of O4f star zeta Puppis. The results of high-resolution spectroscopy for some bright O-stars are also presented. The line profile variability of bright O-stars 19 Cep and lambda Ori A is detected.