Holographic RG is the interpretation of the AdS-CFT correspondence as RG evolution of boundary theory. The radial coordinate is interpreted as the scale of the boundary theory. This allows a new physical way of looking at the correspondence. But, the precise regularisation of the boundary theory that allows this interpretation hasn't been looked at. I will show one such regularisation using ERG formalism. I will write down the ERG equation for the scalar, vector and tensor of boundary O(N) theory. I will explicitly redefine the Exact RG evolution operator that corresponds to this equation as the bulk AdS action, thus making the connection precise. This will be to lowest order in kinetic theory.