Natural　gas　hydrates　(NGH)　as　a　potential　energy　resource　gain　much　attention,　the　depressurization-assisted　CH　4　/CO　2　replacement　is　a　combined　method　proposed　recently　for　NGH　mining.　This　work　experimentally　investigated　the　depressurization-assisted　CH　4　/CO　2　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　CH　4　replacement　ratio　was　increased　by　delaying　the　depressurization　moment　and　increasing　the　depressurization　magnitude.　The　maximum　CH　4　replacement　ratio　reached　61.28%　at　the　depressurization　moment　of　48　h　and　274.15　K.　Additionally,　the　CH　4　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　CO　2　sequestration　when　the　replacement　pressure　is　higher　than　CO　2　hydrate　equilibrium　pressure.　While　it　did　not　facilitate　CO　2　sequestration　when　the　replacement　pressure　is　close　to　CO　2　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　CO　2　/CH　4　replacement　in　the　future.