We have studied the Balmer line shapes of NGC 3516 in order to find the structure of central Emission Line Region (ELR) and the physical parameters of the emitting plasma. The shapes of these broad emission lines show evidences of a multicomponent origin and also features which could be identified as the peaks of a rotating disc. We have proposed a two component Broad Line Region (BLR) model consisting of an inner Keplerian relativistic disc and an outer structure surrounding the disc which is composed by Broad Line and Narrow Line Regions (BLR and NLR). Adopting a mass of ~ 4 x 107 Msun for the central object we found that the emitting disc is located from 0.004 pc to 0.018 pc. Using a well known method for laboratory plasma diagnostic, the Boltzmann plot, we estimated the electron temperature (~12 500 K) and electron density ( ~ 1015 cm-3) of the disc and the surrounding region (Te~ 20 000 K and Ne ~ 1015 cm-3).