In　this　paper,　we　will　develop　new　mathematical　tools　for　mapping　tissue　microstructural　properties　via　the　use　of　space-time　fractional　calculus　methods.　We　propose　the　following　two　new　computational　multi-term　time-space　fractional　diffusion　models　in　three　dimensions,　which　can　be　used　to　simulate　multi-term　time-space　fractional　Bloch-Torrey　models　in　three　dimensions:　Model　I:　Finite　element　method　for　the　multi-term　time-space　fractional　diffusion　model　with　Riesz　fractional　operator;　Model　II:　Finite　difference　method　for　the　multi-term　time-space　fractional　diffusion　equation　with　fractional　Laplacian　operator.　Firstly,　the　three-dimensional　multi-term　time-space　fractional　Bloch-Torrey　models　are　decoupled;　the　problem　is　then　equivalent　to　solving　the　three-dimensional　time-space　fractional　diffusion　equations　(Model　I　and　Model　II).　Secondly,　we　propose　the　finite　element　method　for　Model　I　and　finite　difference　method　for　Model　II,　respectively.　These　methods　can　be　directly　used　to　simulate　three-dimensional　multi-term　time-space　fractional　Bloch-Torrey　models.　Finally,　some　numerical　examples　are　given　to　demonstrate　the　versatility　and　application　of　the　models.