The detection of gravitational waves and their electromagnetic counterpart, events GW170817 and GRB170817A, due to of merging of two neutron stars have revealed that difference between the speed of light and that of gravitational waves are infinitesimal. This difference can be used as a strong constraint on both dark energy and modified gravity models. Here, we focus on different viable f (G) models and determine their parameter space using the combined constraints including GW170817, ρG 0 and equation of state parameter as well as the requirement f,GG > 0. Our results show that the constraint GW170817 can put strong bound on f (G) gravity models.
