Abstract: This paper reports the influence of wetting phenomenon (capillary phenomenon) on the relationship of conversion versus time. The solid particle samples used were four kinds of porous particles with different pore structures. Three different wetting conditions on the results of reaction were defined and studied. The first one is the filling of distilled water into evacuated particles to simulate the ordinary initial conditions of gas-solid reactions. The second one is the filling of the solution used for liquid-solid reaction into evacuated particles. The third case is putting the particles directly into the bulk reaction solution as a general practice of liquid-solid experiments. The experimental results indicated the influence of these three different wetting conditions on the conversion-time relationship and a semi-quantitative analysis was made to describe the conversion under different wetting conditions. Considering the first and the second wetting conditions mentioned above as an initial condition for the unsteady state mass balance equation in a single cylindrical pore, the analytical solutions to the differential equations were obtained. The models obtained can be used not only to fit the present experimental results satisfactorily but also to fit the data taken by previous workers with reaction between slag particles and liquid similar to the system studied in the present work.