Internal relative humidity in concrete is a controlling factor of dying shrinkage. A new measuring system using embedded digital sensors has been developed that provides a convenient and easy way to accurately measuring the internal relative humidity of concrete from very early age. The internal relative humidity and drying shrinkage of non-standard specimen for C30 normal concrete and C60 high performance concrete are measured at drying shrinkage condition. A linear equation between drying shrinkage and internal relative humidity of concrete are established using regression theory.