Radioactive isotopes are extremely useful for determining the age of corals, which can also provide extremely useful archives of past climate change and environmental pollution. In this study, we present a novel approach for dating young corals (<10 a), by applying the ²²⁸Th/²²⁸Ra method. ²²⁸Th/²²⁸Ra disequilibrium was widely observed in a variety of coral genera, from the fringing reefs to atoll reefs in the South China Sea using high-purity germanium γ spectrometry in an aboveground laboratory and China Jinping Underground Laboratory with the deepest carbonate rock overburden in the world. The ²²⁸Th/²²⁸Ra dating method was used to estimate the ²²⁸Th/²²⁸Ra disequilibrium-derived age based on the assumption of the ingrowth of ²²⁸Th from ²²⁸Ra in coral skeletons. To validate the ²²⁸Th/²²⁸Ra dating method, radiogenic (²²⁸Th/²²⁸Ra) and stable isotopes (δ¹⁸O) were measured for the calculations and comparison of the absolute age and relative age in Porites coral skeletons. The ²²⁸Th/²²⁸Ra disequilibrium-derived absolute age was found to be in agreement with the relative age based on the δ¹⁸O curve. We found that the relative uncertainty of the age is simultaneously determined by the relative uncertainties of ²²⁸Th and ²²⁸Ra activities and ²²⁸Th/²²⁸Ra ratio, independent of the analytical methods (α spectrometry, β counter, or γ spectrometry), and is difficult to control. It was demonstrated that the dating range of the ²²⁸Th/²²⁸Ra dating method were constrained by the acceptable value of uncertainty of age. The ²²⁸Th/²²⁸Ra dating method may provide a supplementary approach to the existing coral chronological toolbox of ²¹⁰Pb/²²⁶Ra, ¹⁴C, ²³¹Pa/²³⁵U, and ²³⁰Th/²³⁸U on a time scale from decades and hundreds of years to thousands of years.