Abstract
The S-matrix, its unitarity and the graviton self-energy at the one-loop level are discussed on the basis of quantum Yang-Mills gravity with the translational gauge symmetry in flat space-time. The unitarity and gauge invariance of the S-matrix in a class of gauge conditions is preserved by massless ghost vector particles, called "Feynman-DeWitt-Mandelstam" (FDM) ghosts, in quantum Yang-Mills gravity. Using dimensional regularization, the graviton self-energy is explicitly calculated with a general gauge condition. The resultant divergence of graviton self-energy at the one-loop level resembles that in quantum electrodynamics.