The internal h r values of high performance concrete (HPC) stored in water for 2 years were measured at three different layers(outer layer, middle layer and inner layer). Effects of factors, such as m w/ m c, silica fume and air content on h r values were investigated. Results show that: h r values in the inner and middle layers are reduced with the decrease in m w/ m c and with the increase in the amount of silica fume. The effect of air content on h r values of HPC is negligible; theoretical calculations indicate that the increase in the molar concentration of soluble ions in concrete, and the fractions of inter layer water, absorbed water as well as gel water in the sum evaporable water could be a main reason behind the reduction of h r values or so called self desiccation of HPC with low m w/ m c and silica fume.