A supercritical water oxidation reactor (100, 200, 300, 400, 500, 184, 2000, 2100, 2200), comprising: a housing (101, 201, 301, 401) provided with at least a slurry inlet (1011, 2011, 3011, 4011), an oxidant inlet (1012, 2012, 3012, 4012) and a discharge port (1013, 2013, 3013, 4013), wherein a chamber for providing a reaction zone is formed inside the housing; a heating device (102, 202, 302, 402) configured to increase a temperature in the chamber; and a spiral circulation pipe (103, 203, 303, 403) arranged in the chamber and has an end connected to the slurry inlet (1011, 2011, 3011, 4011), wherein a slurry is introduced into the spiral circulation pipe (103, 203, 303, 403) from the slurry inlet (1011, 2011, 3011, 4011), flows along a pipeline of the spiral circulation pipe (103, 203, 303, 403), and flows out from another end of the spiral circulation pipe (103, 203, 303, 403), wherein after flowing out from the another end of the spiral circulation pipe (103, 203, 303, 403), the slurry is mixed with an oxidant flowing into the chamber from the oxidant inlet, and an oxidation reaction of the slurry and the oxidant occurs, the reactor further comprising: a turn-back tube (204, 304, 404) provided inside the chamber, wherein the turn-back tube (204, 304, 404) comprises an inner tube (2041, 3041, 4041) with both ends open and an outer tube (2042, 3042, 4042) with one end open, the outer tube (2042, 3042, 4042) is sleeved outside the inner tube (2041, 3041, 4041), and the inner tube (2041, 3041, 4041) is in communication with the oxidant inlet (1012, 2012, 3012, 4012), wherein the turn-back tube (204, 304, 404) is arranged at a central axis of the chamber, the reactor further comprising: a stirrer (305, 405) comprising a rotating shaft (3051, 4051), wherein the rotating shaft (3051, 4051) penetrates the housing (101, 201, 301, 401) and extends into the chamber, and/or the rotating shaft (3051, 4051) passes through the discharge port (1013, 2013, 3013, 4013) and extends into the chamber. a housing (101, 201, 301, 401) provided with at least a slurry inlet (1011, 2011, 3011, 4011), an oxidant inlet (1012, 2012, 3012, 4012) and a discharge port (1013, 2013, 3013, 4013), wherein a chamber for providing a reaction zone is formed inside the housing; a heating device (102, 202, 302, 402) configured to increase a temperature in the chamber; and a spiral circulation pipe (103, 203, 303, 403) arranged in the chamber and has an end connected to the slurry inlet (1011, 2011, 3011, 4011), wherein a slurry is introduced into the spiral circulation pipe (103, 203, 303, 403) from the slurry inlet (1011, 2011, 3011, 4011), flows along a pipeline of the spiral circulation pipe (103, 203, 303, 403), and flows out from another end of the spiral circulation pipe (103, 203, 303, 403), wherein after flowing out from the another end of the spiral circulation pipe (103, 203, 303, 403), the slurry is mixed with an oxidant flowing into the chamber from the oxidant inlet, and an oxidation reaction of the slurry and the oxidant occurs, the reactor further comprising: a turn-back tube (204, 304, 404) provided inside the chamber, wherein the turn-back tube (204, 304, 404) comprises an inner tube (2041, 3041, 4041) with both ends open and an outer tube (2042, 3042, 4042) with one end open, the outer tube (2042, 3042, 4042) is sleeved outside the inner tube (2041, 3041, 4041), and the inner tube (2041, 3041, 4041) is in communication with the oxidant inlet (1012, 2012, 3012, 4012), wherein the turn-back tube (204, 304, 404) is arranged at a central axis of the chamber, the reactor further comprising: a stirrer (305, 405) comprising a rotating shaft (3051, 4051), wherein the rotating shaft (3051, 4051) penetrates the housing (101, 201, 301, 401) and extends into the chamber, and/or the rotating shaft (3051, 4051) passes through the discharge port (1013, 2013, 3013, 4013) and extends into the chamber.