The　coexistence　of　highly　toxic　heavy　metal　chromium　and　new　pollutants　microplastics　has　been　widely　present,　and　the　interaction　behavior　and　mechanism　of　the　two　are　crucial　for　their　environmental　effects　in　coexisting　environments,　which　urgently　need　to　be　further　explored.　Firstly,　the　interaction　characteristics　of　polyamide　(PA)　and　polyethylene　(PE)　with　Cr(VI)/Cr(III)　were　investigated,　where　PA　exhibited　higher　adsorption　capacity　of　both　Cr(VI)　and　Cr(III)　than　PE　among　various　environmental　conditions.　The　higher　adsorption　energy　of　PA　on　Cr(VI)/Cr(III)　was　also　achieved　by　DFT　calculation,　and　the　bending　configuration　of　PA　during　the　adsorption　process　may　be　beneficial　for　its　interaction　with　Cr.　Then,　the　combination　of　characterization　analysis　and　DFT　calculation　showed　that　significant　chemical　bonding　occurred　in　the　interaction　between　C--O　bond　of　PA　and　Cr(III),　weak　chemical　interactions　occurred　in　the　adsorption　of　PE　with　Cr(III)　and　PA　with　Cr　(VI),　while　the　adsorption　of　PE　with　Cr(VI)　was　mainly　physical　effects.　This　study　provides　theoretical　support　for　pollution　control　of　microplastics　and　chromium　in　co-existing　environment.