Abstract: Based on the law of energy conservation, the mathematical model considering the effect of heat loss on the hot-wire temperature distribution was developed.The accuracy of the mathematical model was validated by comparing the calculating result with the experimental results.The effect of wire diameter, hot-wire current, wire feeding speed, and wire extension on temperature distribution of hot-wire elaborately was discussed.The results show that the mathematical model has so high accuracy that it can be used to analyze the heating process of wire and satisfies the need of controlling the welding quality.The smaller the wire diameter and wire feeding speed are, the higher the temperature of the position on the wire extension having the same distance away from the power-feeding point is.The higher hot-wire current is, the higher the temperature is.However, the larger the wire extension is, the higher the temperature of the position on the wire having the same distance away from the wire-feeding point is.