The temperature rise of He Ⅱ transfer system due to the negative Joule-Thomson (JT) effect is one of the major problems in the He Ⅱ forced flow system design. Negative Joule-Thomson effect of the He Ⅱ forced flow was analyzed and calculated in this paper. The temperature rise due to the heat leak along the transfer pipeline was calculated by the simplified equation and was modified by considering the negative Joule-Thomson effect. The modified results were compared with the temperature rise obtained by non-linear differential equations with consideration of the pressure gradient. The results show that the pressure gradient has strong effect on the temperature distribution. The modified results are in good agreement with the values calculated by the complicated equation, which verifies the effectiveness of the simplified equation in calculating the temperature rise when the negative JT effect of He Ⅱ is known.