A charge-free conductor cavity has macroscopic quantum effects that can be explained by the physical picture of vacuum zero-point energy. This paper studies the macroscopic quantum effects in the conductive cylindrical ring，in terms of zero-point oscillating modes. The zero-point oscillating modes are obtained through solving the Maxwell equations without sources under the boundary condition of the cylindrical conductor surfaces. The vacuum energy (i.e. the Casimir energy) per unit length and area for the double-layer concentric cylindrical ring is obtained and it can be decomposed into the three independent and convergent parts that come from the interior, exterior cylindrical surfaces and the portion between them, respectively. For an n-layer cylindrical ring, its Casimir energy comprises of (2n-1) parts， all of which are convergent. Topologically, the geometric structure of the cylindrical ring is analogous to that of the parallel plates. However, the Casimir energy of the cylindrical ring has the non-trivial property that the coefficients of the Casimir energies and potentials vary with the interval between the cylindrical surfaces, compared to the constant coefficient for the parallel plates. This non-trivial property will give rise to an additional Casimir force that does not exist in the case of parallel plates.