Symmetric　searchable　encryption　(SSE)　provides　a　secure　and　efficient　way　for　users　to　search　on　the　encrypted　data　stored　on　the　cloud.　Most　of　the　existing　SSE　schemes　reveal　the　search　pattern　and　access　pattern　during　the　query　of　keywords,　which　can　be　used　to　derive　the　keyword　to　query　or　contained　in　documents.　To　solve　this　problem,　we　propose　a　privacy-preserving　multi-cloud　based　dynamic　SSE　scheme,　called　PMD-SSE,　which　implements　the　privacy　protection　and　dynamic　update　of　SSE.　To　protect　the　search　pattern　and　access　pattern,　we　divide　the　index　into　blocks　of　the　same　size　and　distribute　them　to　multiple　clouds,　and　an　index　cache　is　conducted　to　improve　the　efficiency　of　shuffling.　We　shuffle　and　re-encrypt　the　entities　in　index　cache　after　each　query,　and　then　redistribute　them　to　clouds　randomly.　Furthermore,　PMD-SSE　supports　dynamic　update　of　SSE,　and　realizes　the　forward　security　in　dynamic　update　through　the　pseudo-random　function.　At　last,　formal　security　analysis　show　that　PMD-SSE　is　adaptive　secure　against　malicious　attacks.　©　2021　IEEE.