The influence of gate voltage on electron transport in the graphene field-effect transistor under strong laser field is studied by using the finite-difference time-domain method. The perfect tunneling in graphene can be strongly suppressed by the strong laser field induced optical stark effect. This suppression depends not only on the laser field but also on the width and the height of the gate voltage. The electron transport through a non-square barrier is investigated. We find that a barrier with a small incline has little effect on the electron transport, but if the barrier has a large incline, the tunneling probability changes remarkably.