对自干燥条件下混凝土内部相对湿度的变化规律进行理论及试验研究。提出了自干燥效应引起混凝土内部相对湿度与饱水度的函数关系式，采用数字式湿度传感器测量密封养护条件下混凝土内部相对湿度随龄期变化的规律。试验结果表明，低水灰比混凝土早期相对湿度下降非常快，表明低水灰比混凝土早期开裂的几率显著增大。将相对湿度的试验值与本文提出的相对湿度计算模型的计算值进行比较，结果表明，试验值与模型计算值的相对误差非常小。

The functional equations of internal humidity and saturation fraction in concrete induced by self-desiccation effect are presented based on theoretical studies and tests on the relative humidity change in concrete. Digital humidity sensors are used to measure the internal relative humidity change against concrete age under sealed curing. The tests manifest that the relative humidity in concrete with low water-cement ratio decreases rapidly in the early-age, which indicates that the cracking probability of concrete with low water-cement ratio is significantly increased. There is a quite small relative error between the test values of relative humidity and the calculated values from the model proposed in the paper.