The　associative　phase　separation　of　charged　biomacromolecules　plays　a　key　role　in　many　biophysical　events　that　take　place　in　crowded　intracellular　environments.　Such　natural　polyelectrolyte　complexation　and　phase　separation　often　occur　at　nonstoichiometric　charge　ratios　with　the　incorporation　of　bioactive　proteins,　which　is　not　studied　as　extensively　as　those　complexations　at　stoichiometric　ratios.　In　this　work,　we　investigated　how　the　addition　of　a　crowding　agent　(polyethylene　glycol,　PEG)　affected　the　complexation　between　chitosan　(CS)　and　hyaluronic　acid　(HA),　especially　at　nonstoichiometric　ratios,　and　the　encapsulation　of　enzyme　(catalase,　CAT)　by　the　colloidal　complexes.　The　crowded　environment　promoted　colloidal　phase　separation　at　low　charge　ratios,　forming　complexes　with　increased　colloidal　and　dissolution　stability,　which　resulted　in　a　smaller　size　and　polydispersity　(PDI).　The　binding　isotherms　revealed　that　the　addition　of　PEG　greatly　enhanced　the　ion-pairing　strength　(with　increased　ion-pairing　equilibrium　constant　K-a　from　4.92　x　10(4)　without　PEG　to　1.08　x　10(6)　with　200　g/L　PEG)　and　switched　the　coacervation　from　endothermic　to　exothermic,　which　explained　the　promoted　complexation　and　phase　separation.　At　the　stoichiometric　charge　ratio,　the　enhanced　CS-HA　interaction　in　crowded　media　generated　a　more　solid-like　coacervate　phase　with　a　denser　network,　slower　chain　relaxation,　and　higher　modulus.　Moreover,　both　crowding　and　complex　encapsulation　enhanced　the　activity　and　catalytic　efficiency　of　CAT,　represented　by　a　2-fold　increase　in　catalytic　efficiency　(K-cat/K-m)　under　100　g/L　PEG　crowding　and　CS-HA　complex　encapsulation.　This　is　likely　due　to　the　lower　polarity　in　the　microenvironment　surrounding　the　enzyme　molecules.　By　a　systematic　investigation　of　both　nonstoichiometric　and　stoichiometric　charge　ratios　under　macromolecular　crowding,　this　work　provided　new　insights　into　the　complexation　between　natural　polyelectrolytes　in　a　scenario　closer　to　an　intracellular　environment.