A covariant canonical gauge theory of gravity free from torsion is studied. Using a metric conjugate momentum and a connection conjugate momentum, which takes the form of the Riemann tensor, a gauge theory of gravity is formulated, with form-invariant Hamiltonian. Through the introduction of the metric conjugate momenta, a correspondence between the Affine-Palatini formalism and the metric formalism is established. For, when the dynamical gravitational Hamiltonian HDyn does not depend on the metric conjugate momenta, a metric compatibility is obtained from the equation of motions and the energy momentum is covariant conserved. When the gravitational Hamiltonian HDyn depends on the metric conjugate momentum, an extension to the metric compatibility comes from the equation of motion and the energy momentum covariant conservation is violated. For a sample of the HDyn which consists of a quadratic term of the connection conjugate momentum, the effective Lagrangian has the Einstein Hilbert term with a quadratic Riemann term in the second order formalism.