The invention provides a temperature-rising estimating method of a signal wire of a printed circuit board, which includes the following steps: receiving a parameter selected and inputted by a user, carrying out calculation according to the parameter selected and inputted by the user, calculating out the resistance value and the voltage decrease amount of the signal wire in the temperature rising of the signal wire, receiving at least one temperature rising inputted by the user, and drawing the relationship figure of wire width and current according to the received temperature rising. The invention also provides a temperature-rising estimating system of a signal wire of a printed circuit board. The temperature rising of a signal wire of a printed circuit board can be rapidly and accuratelyestimated by using the temperature-rising estimating system and the method of a signal wire of a printed circuit board.