Abstract: Based on the refined zig-zag theory, this paper presents a six-node triangular conforming plate element in combination with finite element formulation for free vibration problems. Different from previous zig-zag theories, the first derivative of transverse displacement has been taken out from the in-plane displacement fields in the refined zig-zag theory, so that the C⁰ shape functions are only required during its finite element implementation. To verify the performance of the presented finite element, typical free vibration problems of soft-core sandwich plates are considered. Numerical results show that the presented triangular conforming plate element is able to accurately predict the natural frequencies of sandwich plates with soft core. However, the nonconforming plate element based on the previous zig-zag theory remarkably underestimates the natural frequencies of soft-core sandwich plates.