The　problem　of　target　detection　and　localization　in　two-layered　media　can　be　solved　by　time　reversal　and　reverse　time　migration　mixed　method.　This　paper　is　extended　from　two-layer　layered　medium　to　three-layered　media.　Due　to　the　interference　of　two　interfacial　reflection　signals,　three-layered　media　is　more　difficult　to　detect　than　two-layer　media.　The　single　prominent　mountain　like　acoustic　field　distribution　is　obtained　around　the　target.　For　interface　reflected　signal,　it　is　a　disordered　and　inhomogeneous　acoustic　field　distribution　with　a　smaller　amplitude.　The　position　of　summit　is　the　just　position　of　the　target,　thus　achieving　the　detection　and　positioning　of　the　target.