Corresponding to the similarity between the Lorentz gauge ∂ µ A µ = 0 in electrodynamics and g µν Γ ρ µν = 0 in gravity, we show that the counterpart of the radiation gauge ∂ i A i = 0 is g ij Γ ρ ij = 0, in stead of other forms as discussed before. Particularly: 1) at least for a weak field, g ij Γ ρ ij = 0 fixes the gauge completely and picks out exactly the two physical components of the gravitational field;2) like A 0 , the non-dynamical components h 0µ are solved instantaneously; 3) gravitational radiation is generated by the "transverse" part of the energy-momentum tensor, similar to the transverse current J ⊥ . This "true" radiation gauge g ij Γ ρ ij = 0 is especially pertinent for studying gravitational energy, such as the energy flow in gravitational radiation. It agrees with the transverse-traceless (TT) gauge for a pure wave, and reveals remarkably how the TT gauge can be adapted in the presence of source.