UBV RI and H$alpha$ photometry has been performed for the open cluster NGC 6531. A total of 56 bright main sequence (MS) members were selected from their positions in photometric diagrams. We also classified 7 pre-main sequence (PMS) stars and 6 PMS candidates with Ha: emission from H$alpha$ photometry. We determined a reddening of < E(B - V) >= 0.29 $pm$ 0.03 and a distance modulus of Vo - Mv = 10.5 for the cluster. From the comparison of our photometric results to theoretical evolution models, we derived a MS turnoff age of 7.5 Myr and a PMS age spread of $~$4 Myr. The IMF slope $Gamma$, calculated in the mass range of 0.45 $le$ log m $le$ 1.35 is a steep value of $Gamma$ = -1.8 $pm$ 0.6.