As　the　inverse-opal　structure　facilitates　the　separation　of　electron-hole　pairs　and　electron　transfer,　it　may　generate　many　radical　species　with　strong　oxidation　capability.　When　a　low　bias　voltage　was　applied　on　the　TiO2　electrodes　with　inverse-opal　structure,　they　exhibited　more　excellent　photoelectrochemical　properties　and　photoelectrocatalytic　activity　than　TiO2　film　under　simulated　solar　light　irradiation.　When　different　types　of　active　species　scavengers　were　added,　the　different　performances　of　TiO2　photonic　crystals　in　rhodamine　B　degradation　showed　that　besides　(OH)-O-center　dot　and　holes,　which　were　the　main　active　species　in　the　photocatalysis,　O-2(center　dot-)　played　a　vital　role　in　the　photoelectrocatalytic　degradation　process.　Furthermore,　the　stronger　signal　of　(OH)-O-center　dot-trapping　photoluminescence　and　the　variation　in　the　concentration　of　nitroblue　tetrazolium　reflected　that　more　(OH)-O-center　dot　and　O-2(center　dot-)　could　be　generated　in　the　photoelectrocatalysis　than　that　in　the　photocatalysis,　and　O-2(center　dot-)　was　partially　obtained　from　the　cathode　surface.　At　last,　the　roles　active　species　played　in　the　photoelectrocatalytic　and　photocatalytic　processes　were　compared,　and　the　possible　degradation　mechanisms　of　TiO2　photonic　crystals　in　photoelectrocatalytic　and　photocatalytic　systems　were　put　forward,　which　could　provide　a　good　insight　into　the　mechanism　of　photoelectrocatalytic　degradation　on　TiO2　photonic　crystals.