SrThO3 belong to stable perovskites family. Some theoretical works have been performed on this compound. However the pressure effect in the pressure range 0 to 30 GPa was never conducted. This work highlights the importance of the hydrostatic compression on the lattice constant and energy bandgap of the compound. Lattice parameter is found to decrease with increasing pressure. SrThO3 comes out as a direct band gap material. We discussed the effect of pressure on the energy band gap and got to know that overall energy band gap decreases as pressure increases. Finally we discussed the density of states of SrThO3 and plotted it against energy.