Abstract: On the base of fractal theory, a fractal reaction model of shrinking core in irregular particle/ fluid system is developed. A pseudo - steady state equation of material balance and its solution in terms of the concentration profile of reacting fluid and the expressions of reaction time, complete reaction time, relative reaction time the amount of reacting fluid per unit time (and the conversion of the particle) are given in fractal dimension. The reaction time and other parameters at the control stages, such as fluid film diffusion, ash diffusion and chemical reaction, are also derived from the above expressions. The influences of fractal dimensions of particles on the reaction processes are discussed.