利用液氦超流转变时超流氦（He Ⅱ）与正常氦（He Ⅰ）热导率突变的性质复现液氦超流转变温度T_λ。采用带毛细管结构的小型密封瓶，通过控温将微小热流通过小型密封瓶毛细管，实现毛细管中He Ⅰ/He Ⅱ两相共存，并使He Ⅰ/He Ⅱ界面停留在毛细管中，从而获得稳定、平坦的液氦超流转变温坪。利用毛细管热流对液氦超流转变温度的下压效应，得到不同热流的多个温坪，进一步利用外推法求得零热流下真实的T_λ值。24次液氦超流转变温度复现实验结果表明，标准偏差为0.022mK，证明了液氦超流转变温度具有良好的稳定性和复现性，推荐将液氦超流转变温度作为国际温标的固定点使用。

Based upon the dramatic change in thermal conductivity of liquid heliumat at the
temperature of the transition between superfluid (He Ⅱ) and normal fluid (He I), a sealed-cell with a capillary has been used to determine the superfluid transition temperature, T_λ. A controlled small heat flow is passed through the capillary of the sealedcell to realize the coexistence of He I and He Ⅱ and maintain the He Ⅰ/He Ⅱ interface in the capillary. A stable and flat lambda transition temperature plateau is obtained. Because there is a depression of T_λ by the heat flow through the capillary, a series of heat flows and several temperature plateaus are made and an extrapolation is applied to determine T_λ with zero heat flow. A rhodiumiron resistance thermometer with series number of A34（RIRT A34）was used in 24 experiments to determine the superfluidtransition temperature with a standard deviation of 0.022mK, which demonstrates the stability and reproducibility of T_λ. We therefore recommend that superfluid transition temperature of helium be used as a fixed point on the International Temperature Scale.