In dense-phase pneumatic conveying, the solid moisture content can significantly influence the conveying process, but there are very few studies in the open literature. In this study, the conveying experiments of two pulverized coals with various moisture contents were carried out at a 4MPa high pressure and dense-phase pneumatic conveying facility. Results show that the whole conveying system can be stably and controllably operated under the condition that moisture content below ~8%. With the increase of moisture content up to ~8%, the mass flow rate of 280 μm pulverized coal increases at first and then decreases, while that of 55 μm pulverized coal decreases continuously. The method of solid friction factor correlation is used to investigate pressure drop of the horizontal pipe, and non-dimensional parameters--Fr number, moisture content M and solid loading ratio μ--are investigated. The pressure drop predictions by this correlation are in good agreement with the experimental data. The solid friction factor correlations indicate that the fine coal is more sensitive to M, and μ plays a more important role for the coarse coal.