We present the results of the optical spectroscopic analysis and modeling of B1a star rho Leo. We have analysed spectra of rho Leo obtained with the 6-m BTA telescope (Special Astrophysical Observatory, Nizhnij Arkhyz, Russia) using the SCORPIO focal reducer. We obtain the stellar parameters and chemical abundances of rho Leo comparing models with the observed spectra. Model spectra were calculated using non-local thermodynamic equilibrium (non-LTE) radiative transfer code CMFGEN. We find temperature Teff=23500 K, luminosity L = 2.8E5 Lsun, radius R =31 Rsun, mass M =28 Msun, logg=2.88 and mass-loss rate in the range dM/dt=(9.55-15.00)*E-7 Msun/year. We investigate the impact of an enhanced mass loss rate on the Hbeta, Hgamma, and helium line profiles.