Herein,　a　dual　drug-loaded　hydrogel　delivery　system　was　constructed　using　aldehyded　pullulan　(A-Pul),　ϵ-poly-l-lysine　(ϵ-PL),　and　branched　polyethylenimine　(BPEI)　in　an　aqueous　solution　via　a　Schiff　base　reaction.　CDDP　and　DOX　were　loaded　into　the　network　of　hydrogels　for　combination　drug　therapy.　Gelation　time　changed　from　40　s　to　240　s　when　reaction　solutions　were　stored　at　different　temperatures.　Scanning　electron　microscopy　images　and　swelling　dynamics　demonstrated　that　the　hydrogels　had　a　homogeneous　porous　structure　and　good　swelling　behavior.　The　in　vitro　degradation　rate　and　drug　release　rate　at　pH　7.0　were　faster　than　those　at　pH　7.4;　this　indicated　that　the　hydrogels　displayed　controlled　drug　release　and　pH-dependent　behavior.　The　hydrogels　could　be　injected　and　formed　in　situ　and　degraded　in　vivo,　and　the　dual-drug-loaded　hydrogel　displayed　the　most　efficient　tumor　inhibition;　this　indicated　the　synergistic　anticancer　effect　of　the　CDDP　+　DOX　combination　therapy　in　H22　liver　tumor-bearing　mice.　Furthermore,　the　hydrogels　displayed　no　cytotoxicity　against　Huh-7　cells　and　exhibited　excellent　security　and　biocompatibility　in　vivo.　Therefore,　the　hydrogels　have　potential　applications　as　multidrug　carriers　for　enhanced　synergistic　therapy.　©　2017　The　Royal　Society　of　Chemistry.