Effects of toroidal flows on ballooning mode instabilities have been studied extensively in recent years. In the published works, toroidal flow effects are taken into account only in the perturbation equation while the tokamak equilibrium is assumed to be unchanged. In this work, the influence of a toroidal flow on ballooning mode instabilities is numerically investigated by using the BOUT++ code while the modification of the tokamak equilibrium due to the flow has been taken into account in fixing the profiles of the quasi-toroidal magnetic field, quasi-density, and quasi-pressure and only changing the toroidal Mach number. A toroidal flow can significantly modify the safety factor q profile and the pressure gradient del P, which then affects the ballooning instability. The simulation results show that in the presence of shear flows, the growth rate of the ballooning mode will be affected if the modified equilibrium is considered. For a shear flow, the growth rates of high-n modes are significantly reduced.