alpha-L-fucosidases　(EC　3.2.1.51,　FUC),　belonging　to　the　glycoside　hydrolase　family　29　(GH29),　play　important　roles　in　several　biological　processes　and　are　markers　used　for　detecting　hepatocellular　carcinoma.　In　this　study,　a　protein　sequence　similarity　network　(SSN)　was　generated　and　a　subsequent　evolutionary　analysis　was　performed　to　understand　the　enzymes　comprehensively.　The　SSN　indicated　that　the　proteins　in　the　FUC　family　are　mainly　present　in　bacteria,　fungi,　metazoans,　plants,　as　well　as　in　archaea,　but　less　abundantly.　The　sequences　in　bacteria　were　found　to　be　more　diverse　than　those　in　other　taxonomic　groups.　The　SSN　and　a　phylogenetic　tree　both　supported　that　the　proteins　in　the　FUC　family　can　be　classified　into　3　subfamilies.　FUCs　in　each　subfamily　are　under　the　pressure　of　negative　selection.　The　enzymes　from　metazoans,　fungi,　and　plants　separated　into　the　three　subfamilies　and　shared　high　similarity　with　the　bacterial　homologs.　The　multiple　sequence　alignment　results　indicated　that　the　amino　acid　residues　for　binding　alpha-L-fucosidase　and　catalysis　are　highly　conserved　in　the　3　subfamilies;　however,　the　evolutionary　patterns　were　different,　based　on　the　coevolution　analysis　in　the　subfamily　of　metazoans　and　bacteria.　Finally,　gene　duplication　plays　an　important　role　for　alpha-L-fucosidase　evolution,　not　only　in　metazoans,　but　also　in　bacteria　and　fungi.