Autothermal　reforming　(ATR)　is　an　effective　route　for　hydrogen　production　from　acetic　acid　(HAc)　derived　from　biomass.　Ni-based　catalysts　are　promising　candidates　for　ATR　due　to　their　high　activity,　but　coke　formation　hinders　their　practical　application.　To　tackle　this　issue,　a　series　of　Ni-Mg-Cr　catalysts　with　supports　of　Cr2O3　or　MgCr2O4　were　prepared　by　the　sol-gel　method　and　evaluated　in　ATR.　The　results　indicated　that　as　compared　to　the　Ni-Cr2O3　catalyst,　the　Ni0.25Mg0.75CrO3.5　+/-delta　catalyst　with　MgCr2O4　support　presented　higher　catalytic　performance:　the　conversion　rate　of　acetic　acid　was　stable　near　100%,　with　hydrogen　yield　reaching　2.64　mol-H2/mol-HAc　during　a　40　h　ATR　test,　while　there　was　no　obvious　coking.　It　was　found　that　Mg　modification　was　prone　to　constituting　a　stable　MgCr2O4　spinel　support　with　a　high　specific　surface　area　for　adsorption　and　transformation　of　HAc;　however,　for　catalysts　with　excessive　Mg　addition,　namely,　Ni0.43Mg2.56CrO4.5　+/-delta　and　Ni0.69Mg5.31CrO7.5　+/-delta,　low　reactivity　was　found　and　was　linked　to　constraining　of　Ni　from　the　solid　solution　of　Mg(Ni)O.　Density　functional　theory　(DFT)　calculations　reveal　that　during　the　ATR　process,　Ni4-MgCr2O4　presents　a　low　energy　barrier　for　the　overall　transformation　path　and　a　high　stabilization　of　reaction　intermediates;　furthermore,　as　compared　to　Ni4-Cr2O3,　oxidation　of　C*　species　by　O*　and　OH*　is　significantly　accelerated　on　Ni4-MgCr2O4　due　to　the　considerably　decreased　energy　barriers,　thus　eliminating　carbon　deposition　and　improving　catalytic　activity.