Tumor　metastasis　with　resistance　to　anticancer　therapies　is　the　main　cause　of　death　in　cancer　patients.　It　is　necessary　to　develop　reliable　tumor　metastasis　models　that　can　closely　recapitulate　the　pathophysiological　features　of　the　native　tumor　tissue.　In　this　study,　chondroitin　sulfate　(CS)-modified　alginate　hydrogel　beads　(ALG-CS)　are　developed　to　mimic　the　in　vivo　tumor　microenvironment　with　an　abnormally　increased　expression　of　CS　for　the　promotion　of　tumor　cell　metastasis.　The　modification　mechanism　of　CS　on　alginate　hydrogel　is　due　to　the　cross-linking　between　CS　and　alginate　molecules　via　coordination　of　calcium　ions,　which　enables　ALG-CS　to　possess　significantly　different　physical　characteristics　than　the　traditional　alginate　beads　(ALG).　And　quantum　chemistry　calculations　show　that　in　addition　to　the　traditional　egg-box　structure,　novel　asymmetric　egg-box-like　structures　based　on　the　interaction　between　these　two　kinds　of　polymers　are　also　formed　within　ALG-CS.　Moreover,　tumor　cell　metastasis　is　significantly　enhanced　in　ALG-CS　compared　with　that　in　ALG,　as　confirmed　by　the　increased　expression　of　MMP　genes　and　proteins　and　greater　in　vitro　invasion　ability.　Therefore,　ALG-CS　could　be　a　convenient　and　effective　3D　biomimetic　scaffold　that　would　be　used　to　construct　standardized　tumor　metastasis　models　for　tumor　research　and　anticancer　drug　screening.