The invention discloses a seamless steel tube perforator piercing point on-line regulating device, which comprises a piercing rod and a piercing rod trolley, wherein the piercing point is at one end of the piercing rod and is a cone; the terminal line of the cone is a straight line with transitional curves at two ends; and the other end of the piercing rod is arranged on the piercing rod trolley. The seamless steel tube perforator piercing point on-line regulating device is characterized by also comprising a locking device, wherein the position of the piercing rod trolley is locked by the locking device; when the piercing point presses a tube blank of a seamless steel tube, the locking device can move the locked position of the piercing rod trolley along the moving direction of the tube blank, so that the piercing rod can move together with the piercing rod trolley by means of a rolling force. According to the device, the piercing point can move along the moving direction of the tube blank in a tube blank perforation process, so that the outside diameter of the piercing point in a tube blank perforating forming region can be reduced to compensate for the increase of the outside diameter of the piercing point with heat expansion in the tube blank perforation process; and thus, the outside diameter of the piercing point in the tube blank perforating forming region can keep stable and constant, and the inside diameter of a tubular billet formed by tube blank perforation is not changed.