Abstract: In theory,the extension of a discontinuity trace in revealing detailed map of the excavated surface by rock slope design must be in accordance with the pitch of the intersecting line of discontinuity and excavated surface on the latter.Grasping the pitch regularity and manipulating the appropriate sketch technique maybe not only make the trace map coincide with the in-site actual situation,but also increase drawing efficiency and data quality,without no avail of the accurate analysis for slope structure model.In view of this,by means of in-site observation and conclusion,relationships between discontinuity and slope surface and properties of discontinuities traces are analyzed.Based on formulas to express pitch rules,the discriminance of pitching by features triangle,which is inferred from both attitudes of discontinuity and slope surface,is proposed.Meanwhile,nomograph to determine pitch of discontinuity trace is drawn up.Under the proper condition,checking and concluding one of essentials of attitude by other one is discussed.Practical application of pitch regularity to a particular case,the trace of which is difficult to draw,is illustrated.