Natural　gas　hydrates　(NGH)　as　a　potential　energy　resource　gain　much　attention,　the　depressurization-assisted　CH4/CO2　replacement　is　a　combined　method　proposed　recently　for　NGH　mining.　This　work　experimentally　investigated　the　depressurization-assisted　CH4/CO2　replacement　behavior　in　the　muddy-silt　slurries,　and　the　effect　of　depressurization　moment,　amplitude　and　frequency　was　systematically　examined.　The　results　revealed　that　the　depressurization　after　replacement　significantly　promoted　reaction　within　a　short　period.　The　CH4　replacement　ratio　was　increased　by　delaying　the　depressurization　moment　and　increasing　the　depressurization　magnitude.　The　maximum　CH4　replacement　ratio　reached　61.28%　at　the　depressurization　moment　of　48　h　and　274.15　K.　Additionally,　the　CH4　replacement　ratio　was　further　increased　in　the　secondary　depressurization　event　compared　to　that　at　the　primary　depressurization.　This　research　indicated　that　the　depressurization　was　beneficial　for　CO2　sequestration　when　the　replacement　pressure　is　higher　than　CO2　hydrate　equilibrium　pressure.　While　it　did　not　facilitate　CO2　sequestration　when　the　replacement　pressure　is　close　to　CO2　hydrate　equilibrium　pressure.　The　free　water　consumption　decreased　with　the　increase　of　the　depressurization　moment,　amplitude　and　frequency.　These　findings　would　contribute　to　the　development　of　the　depressurization-assisted　CO2/CH4　replacement　in　the　future.　©　2024　Elsevier　B.V.