By the tight-binding method, we study the transport properties of right-angle L-shaped graphene nanoribbons. We found a universal conclusion is that the resonance of electron tunneling will present at the Dirac point when the system is metallic and the ribbons widths satisfy (NBAB=2NBZB-1). Further research suggests that the conductance resonance effect will be destroyed by impurity scatterer, especially the impurity concentration and strength are nontrivially large. We also found that antiresonance effect will result in a strong conductance suppression when the width difference () of the two ribbons is very big. In addition, when the system is semiconducting, the center of the well-defined insulating band can be easily tuned by a gate bias exerted on the armchair-edged graphene nanoribbon.