Rock slope stability analysis is a probabilistic problem. The equivalent linear parameters derived from the Hoek-Brown criterion and the jointly distributed random variables methods are used to determine the probability distribution of the safety factor. The program from the Matlab is provided to take place of the calculation. The result confirms the feasibility of the jointly distributed random variables method and shows that the safety factor approximately obeys the normal distribution. The jointly distributed random variables method can provide a rapid evaluation. Besides,the sensitivity analysis to the parameters shows that the more effective parameter is the horizontal seismic acceleration rather than the water depth of the tension crack.