The distribution of water pressure in different fractured rock masses is different.It is important to study the water pressure distribution to the analysis of slope stability.Problems are existed in the distribution law of the traditional fissure water pressure distribution.A reasonable law of water pressure distribution is proposed for several special cases.The stability of wedge rock slope is analyzed by Swedge software in different water pressure distribution and with tension crack whether or not.The results show that the stability of wedge with tension crack is lower than without tension crack when the wedge discontinuity without water pressure distribution.The distribution of water pressure has a great influence on the stability of wedge.The distribution of water pressure in different discontinuity is different.If it is calculated in the form of uniform water pressure distribution，there will be a lot of error.