The　commercialization　of　Ni-based　catalysts　in　CO2　dry　reforming　of　methane　(DRM)　suffers　from　their　quick　deactivation.　Here,　we　reveal　each　reaction　pathway　for　DRM　based　on　the　Ni　catalyst　composition　and　geometry　under　working　conditions,　through　one　working　platform　combining　in　situ　high　resolution　Cs　corrected　environmental　transmission　electron　microscopy　and　electron　energy-loss　spectroscopy　coupled　with　mass　spectroscopy.　The　formation　of　Ni3C　has　been　found　to　inhibit　the　decomposition　of　CO2　and　CH4,　and　to　promote　the　formation　of　onion-like　carbon　to　encapsulate　the　Ni　catalysts,　leading　to　the　deactivation　of　the　Ni-based　catalysts.　Designing　the　suitable　supports　or　promoters　to　keep　the　Ni　surface　structure　under　Ni-NiO　cycle　can　drive　the　simultaneously　amorphous　carbon　deposition-consumption　cycle　and　minimise　the　coke　formation.　This　research　is　not　only　for　developing　coke　resistance　Ni　catalysts　in　the　DRM,　but　also　significant　for　investigating　many　catalysis　challenges　both　in　research　and　engineering.