The　heating　mechanism　of　standing　surface　acoustic　waves　(SSAWs)　on　a　LiNbO3　substrate　has　been　experimentally　studied.　Three　devices　with　different　substrates　were　used　to　heat　the　drops　with　NaCl　concentrations　ranging　from　0　to　1　g/l,　respectively.　The　device　with　a　glass　substrate　was　used　to　shield　acoustic　waves.　The　device　with　an　Au　layer　between　the　LiNbO3　substrate　and　the　droplet　was　used　to　shield　the　alternating　current　field.　The　results　show　that　the　thermal　effect　induced　by　SSAWs　on　the　LiNbO3　substrate　is　composed　of　the　acoustothermal　effect　due　to　SSAWs　and　the　electric　field　thermal　effect　(Joule　heat)　due　to　the　alternating　current　field.　The　electric　field　thermal　effect　which　is　ignored　in　SSAW　devices　previously　plays　an　important　role　in　the　thermal　effect　induced　by　SSAWs.　These　results　provide　a　meaningful　insight　into　the　mechanism　of　SSAW-based　heating,　which　is　of　great　help　to　guide　the　effective　use　of　the　SSAW-based　heating　technique　for　various　applications.　Published　by　AIP　Publishing.