Currently,　colloidal　quantum　dots　(CQDs)　photodetectors　have　shown　significant　advancement　in　the　field　of　infrared　photodetection.　However,　the　immature　analysis　of　dark　current　components　hinders　the　realization　of　higher　performance　quantum　dots　optoelectrical　devices.　In　this　study,　based　on　a　PbS　CQD　photodetector,　we　employ　a　conventional　dark　current　model　of　infrared　photodetectors　to　analyze　the　dark　current　components　of　the　device,　yielding　fitting　results　highly　consistent　with　experimental　observations.　Our　findings　indicate　that　with　increasing　reverse　bias,　the　dominant　dark　current　components　of　the　PbS　CQD　photodetector　shift　from　diffusion　(Diff)　current,　generation-recombination　(G-R)　current,　and　shunt　(sh)　current　to　trap-assisted　tunneling　(TAT)　current.　The　band　diagrams,　recombination　rates,　carrier　density　distributions,　and　electric　field　intensity　maps　under　different　biases　are　further　simulated,　of　which　the　theoretical　results　confirm　that　current　components　transition　is　attributed　to　the　abundance　of　defects　in　quantum　dot　materials,　leading　to　tunneling　at　the　interface　between　the　SnO2　layer　and　PbS-I　layer　under　high　bias　conditions.　Our　work　contributes　to　providing　insight　and　direction　for　optimizing　the　CQD　photodetector　performances.