We have studied the electronic structures, ferromagnetic properties, half-metallicity and exchange splitting in BaO doped with titanium such as Ba1-xTixO at concentration x = 0.125. The structural parameters of BaO and Ba0.875Ti0.125O compounds are calculated with generalised gradient approximation of Wu and Cohen, while their electronic structures, accurate band gaps and magnetic properties are evaluated by the use of the Tran-Blaha-modified Becke-Johnson potential. The changes of lattice parameter and bulk modulus of Ba0.875Ti0.125O are discussed with respect to the BaO. We have found that the Ba0.875Ti0.125O has a wide half-metallic ferromagnetic gap of 2.701 eV and a half-metallic gap of 0.803 eV with integral Bohr magneton of 2 μB, where its ferromagnetic state is characterised by the main contribution of the direct exchange splitting. Therefore, the Ba0.875Ti0.125O is true half-metallic ferromagnet with spin polarisation of 100 % and appears to be promising material for spintronics applications.