A punch pin assembly, comprising: a punch rod, the punch rod internally having a first heat-conducting medium conveying channel and a second heat-conducting medium conveying channel; the first heat-conducting medium conveying channel and the second heat-conducting medium conveying channel communicating with the outside of the punch rod separately through a first medium port and a second medium port which are formed in the punch rod; a punch pin connection rod, the punch pin connection rod internally having an acting heat-conducting medium conveying channel; two ends of the acting heat-conducting medium conveying channel extending out of the punch pin connection rod and communicating with the first heat-conducting medium conveying channel and the second heat-conducting medium conveying channel respectively to form a heat-conducting medium conveying loop; and a punch pin, the punch pin connected to the punch rod through the punch pin connection rod, wherein at least one portion of the acting heat-conducting medium conveying channel is disposed in a way of achieving heat transfer with the punch pin; the first medium port or the second medium port communicates with a low-temperature heat-conducting medium source to receive a heat-conducting medium for cooling the punch pin; characterized in that sealing rings are mounted and face seals (11; 7) are formed between the punch rod and the punch pin connection rod as well as between the punch pin connection rod and the punch pin; and that the first medium port and the second medium port are arranged at the first end of the punch rod in an adjacent manner; the first end of the punch rod is opposite to the second end of the punch rod; and the punch pin connection rod is connected to the second end of the punch rod; wherein a distance from the face seal between the punch rod and the punch pin connection rod to the first end of the punch rod is shorter than a distance from the sealing ring between the punch rod and the punch pin connection rod to the first end of the punch rod; and/or a distance from the sealing ring between the punch pin connection rod and the punch pin to the first end of the punch rod is shorter than a distance from the face seal between the punch pin connection rod and the punch pin to the first end of the punch rod. a punch rod, the punch rod internally having a first heat-conducting medium conveying channel and a second heat-conducting medium conveying channel; the first heat-conducting medium conveying channel and the second heat-conducting medium conveying channel communicating with the outside of the punch rod separately through a first medium port and a second medium port which are formed in the punch rod; a punch pin connection rod, the punch pin connection rod internally having an acting heat-conducting medium conveying channel; two ends of the acting heat-conducting medium conveying channel extending out of the punch pin connection rod and communicating with the first heat-conducting medium conveying channel and the second heat-conducting medium conveying channel respectively to form a heat-conducting medium conveying loop; and a punch pin, the punch pin connected to the punch rod through the punch pin connection rod, wherein at least one portion of the acting heat-conducting medium conveying channel is disposed in a way of achieving heat transfer with the punch pin; the first medium port or the second medium port communicates with a low-temperature heat-conducting medium source to receive a heat-conducting medium for cooling the punch pin;