The direct and historical observation of gravity resulting from the merger of black holes by LIGO has opened a whole new window on the universe, allowing us to experiment with gravity and strong gravitational fields. As a result, the tendency to discuss the problems and complex quasinormal modes of black holes has recently increased. In this paper, we consider a black hole in F(R) gravity. We will study the perturbation equation and effective potential using the Regge-Wheeler gauge. The fundamental characteristic quasinormal modes of this black hole have been calculated for gravitational field perturbation by using the sixth-order WKB approximation approach.