The calculation and analysis of jointed strata stability surface is a question worth study and discussion. On tha basis of jointed structure feature and time effectiveness feature of jointed strata deformation,two elastic-vis-co-plastic mathematical models for discontinuous and continuous jointed rock strata are established and a calculrtion method of slope safety level in jointed rock mass is proposed, laboratory model checking computation as well as field case calculation and analysis proved the mathematical models and theoretical analysis to be rational and reliable.