The humidity field of shotcrete with an alkali-free or alkaline accelerator was measured under sealed or drying conditions. The pore structures of the cement paste were characterized, and the influence of the accelerators on water-transmission characteristics and humidity change in the shotcrete was identified. The results show that the use of an accelerator increases the water loss rate under drying conditions, resulting in a lower internal humidity and a higher humidity gradient in shotcrete. The alkaline accelerator has a greater impact on the internal moisture of the shotcrete than the alkali-free accelerator, as the accelerator reacts with cement particles to produce a large number of rod-shape hydration products (Ettringite), resulting in the increase of pore size and cumulative porosity in cement, and the effect is stronger for the longer age (28 d) samples. The diffusion coefficient of shotcrete with an accelerator was determined and found to be significantly higher than that of the control group. The diffusion coefficient with an alkaline accelerator was slightly higher than the sample with an alkali-free accelerator. The calculated humidity was in a good agreement with the experimental data.