The semi-detached eclipsing binary system BP Muscae has been analysed using the Wilson-Devinney program. Light curves have been obtained in the GENEVA 7-colour photometric system, and radial velocity curves for both components have been measured with the spectrograph CORALIE. The physical and orbital parameters have been determined through a self-consistent simultaneous solution of light curves in seven colours and of the radial velocity curves of both components. The absolute elements of the components are, for the primary (mass gainer), M-1 = 2.40 +/- 0.01 M., R-1 = 2.64 +/- 0.01 R., M-bol1 = 0.66 +/- 0.04, T-eff1 = 9180 +/- 90 K, and for the secondary (mass loser), M-2 = 0.68 +/- 0.01 M., R-2 = 3.76 R., M-bol2 = 2.40 +/- 0.08, T-eff2 = 5160 +/- 90 K. The semi-major axis A of the relative orbit is 13.617 +/- 0.019 R, The spectral type of the components are A0.5/1.5 V (primary) and about G5 III. The distance to BP Mus is evaluated as 562 +/- 17 pc, and the colour excess E[B2-V1] as 0.220 +/- 0.014.