The spectrum of platinum was observed in the (300 to 2100) A wavelength region. The (5d5 + 5d46s) - 5d46p transition array of five times ionized platinum, Pt VI, has been investigated and 1390 spectral lines have been classified in the region of (399 to 1564) A. The analysis has led to the determination of the 5d5, 5d46s and 5d46p configurations. All 37 theoretically possible 5d5 levels, 46 of 63 possible 5d46s levels and 167 of 180 possible 5d46p levels have been established. The orthogonal operators technique was used to calculate the level structure and transition probabilities. The energy parameters have been determined by the least squares fit to the observed levels. Calculated transition probability and energy values, as well as LS-compositions obtained from the fitted parameters are presented. The uncertainties of the established energy levels and calculated (Ritz) wavenumbers are included.