When　the　stress　wave　propagates　through　rock　mass　with　different　wave　impedances　on　two　sides.　It　shows　different　reflection　tendencies　compared　with　the　traditional　study　of　wave　propagation.　A　characteristic　line　method　combined　with　the　displacement　discontinuity　model　was　proposed　to　study　the　wave　reflection　through　such　rock　mass.　The　effects　of　incident　frequency,　joint　stiffness　and　wave　impedance　ratio　on　the　reflection　coefficient　were　discussed.　The　results　show　that　the　reflection　coefficient　increases　as　the　wave　impedance　ratio　increases.　The　traditional　study　of　wave　reflection　can　be　regarded　as　a　special　case　of　the　present　study　when　the　wave　impedance　ratio　equals　1.0.　Moreover,　the　difference　of　reflection　coefficients　decreases　as　the　incident　frequency　increases,　while　increases　as　the　joint　stiffness　and　wave　impedance　ratio　increase　when　the　wave　impedance　ratio　is　larger　than　1.0.　When　the　wave　impedance　ratio　is　smaller　than　1.0,　the　difference　of　reflection　coefficients　increases　firstly　and　then　decreases　with　the　increase　of　incident　frequency　and　joint　stiffness,　while　decreases　as　the　wave　impedance　ratio　increases.　For　the　cases　of　large　incident　frequency　or　small　joint　stiffness,　the　effects　of　wave　impedance　ratio　can　be　neglected　for　the　approximated　prediction　of　wave　reflection.