A thermostatic faucet, comprising a metal housing, a plastic inner body disposed in the metal housing, a plastic valve rod and a plastic shaft seat which are connected in the plastic inner body, a flow valve core and a thermostatic valve core which pass through the metal housing and are mated with the plastic valve rod and the plastic shaft seat respectively, wherein the plastic inner body is provided with a first water inlet connector, a second water inlet connector and a water outlet connector, the first water inlet connector, the second water inlet connector and the water outlet connector are integrally formed with the plastic inner body; the first water inlet connector is connected with the plastic shaft seat through a chamber of the plastic inner body to form a first water inlet passage, the second water inlet connector is connected with the plastic shaft seat to form a second water inlet passage; one of the first water inlet passage and the second water inlet passage is a hot water passage, the other of the first water inlet passage and the second water inlet passage is a cold water passage; and the plastic valve rod cooperates with the plastic inner body to form a chamber communicated with the water outlet connector to form a water outlet passage wherein the plastic inner body has a first chamber, a second chamber, a third chamber and a mating chamber therein, the second chamber, the third chamber and the mating chamber communicate with each other, the mating chamber is connected between the second chamber and the third chamber; the plastic valve rod is accommodated in the second chamber, one end of the plastic valve rod is connected to one end of the mating chamber; the plastic shaft seat is fitted in the third chamber and has one end connected to another end of the mating chamber; one end of the first chamber communicates with the plastic shaft seat in the third chamber, another end of the first chamber is provided with a plug; the first water inlet connector is connected with the plastic shaft seat through the first chamber to form the first water inlet passage; an inner chamber of the plastic shaft seat, the mating chamber and an inner chamber of the plastic valve rod form a mixed water passage, the plastic valve rod cooperates with the second chamber to form a water outlet chamber, and the water outlet chamber communicates with the water outlet connector to form the water outlet passage, wherein the metal housing includes a front housing and a rear end cover to mate and connect with each other, and two ends of the front housing are formed with mating holes (112, 113) for insertion of the flow valve core and the thermostatic valve core, respectively, wherein the flow valve core passes through the mating hole at one end of the front housing and is partially accommodated in the second chamber of the plastic inner body and connected with the plastic valve rod and then is fixed by a metal sealing lid, wherein the metal sealing lid is provided with a screw portion, the screw portion is inwardly reduced to form a reduced portion, the metal sealing lid is sleeved on the flow valve core, the reduced portion is connected in the second chamber of the plastic inner body, and the screw portion is screwed with the mating hole, the thermostatic faucet being characterized in that a stepped surface formed between the screw portion and the reduced portion is pressed against the plug of the plastic inner body.