In this paper, self trapping of a focused optical beam through BaTiO 3 with some external field has been theoretically studied. We find that it is unsuitable for observation of the spatial solitons in conventional cut crystals, in which only the small electro optical coefficent γ 33 is useful. By invesgating self trapping in special cut crystals, the range of the external field for self trapping of the beam and the optimal angle have been given.