Abstract: Although foam drilling has a good capacity of transporting cuttings, but in horizontal well drilling, there also exists a problem in cuttings transportation in the annulus. To efficiently reduce or clear up cuttings-bed is critical to successful drilling. According to the mass conservation law and the momentum conservation theorem, the mixed flow of the foam and cuttings in the annulus is stimulated by using the method of computation fluid dynamics of FLUENT software. So the variation rules of the foam quality in the eccentric annulus and the height of cuttings-bed at annulus velocity are obtained. Also the rules are compared with the cuttings carrying capacity of conventional drilling fluid. Research results show that foam drilling fluid has strong cuttings transporting capacity, and the cuttings-bed in horizontal sections is lower than that under normal mud conditions. The foam quality and annulus velocity exerts great effect on cuttings transportation.