Wireless　sensor　networks　(WSNs)　have　become　increasingly　popular　due　to　the　rapid　growth　of　the　Internet　of　Things.　As　open　wireless　transmission　media　are　easy　to　attack,　security　is　one　of　the　primary　design　concerns　for　WSNs.　Current　solutions　consider　routing　and　data　encryption　as　two　isolated　issues,　providing　incomplete　security.　Therefore,　in　this　paper,　we　divide　the　WSN　communication　process　into　a　data　path　selection　phase　and　a　data　encryption　phase.　We　propose　an　improved　transmission　method　based　on　ant　colony　optimization　(ACO)　and　threshold　proxy　re-encryption　for　WSNs,　and　we　named　it　as　ACOTPRE.　The　method　resists　internal　and　external　attacks　and　ensures　safe　and　efficient　data　transmission.　In　the　data　path　selection　stage,　the　ACO　algorithm　is　used　for　network　routing.　The　improvement　of　the　pheromone　concentration　is　proposed.　In　order　to　resist　attacks　from　external　attackers,　proxy　re-encryption　is　extended　to　WSN　in　the　data　encryption　stage.　The　threshold　secret　sharing　algorithm　is　introduced　to　generate　a　set　of　re-encryption　key　fragments　composed　of　random　numbers　at　the　source　node.　We　confirm　the　performance　of　our　model　via　simulation　studies.　©　The　Author(s)　2022.