飞秒激光与金属作用后，电子被瞬间加热，电子温度将远远高于声子温度，并逐渐将能量传递给声子，这种非平衡过程中电子和声子间传热能力由电子声子耦合系数表征。而到目前为止电子声子耦合系数是否存在尺度效应还存在争议。采用飞秒激光抽运探测法对金纳米薄膜非平衡传热过程进行了研究，利用抛物两步模型对实验数据进行拟合。通过对不同厚度的金纳米薄膜的电子声子耦合系数的比较，研究表明，电子声子耦合系数随着薄膜厚度的增加而减小。实验结果与已报道的基于电子自由程提出的理论模型所预测的变化趋势相一致。

After femtosecond laser exciting the metals, photons excite electrons into higher energy levels, and then the excited electrons thermalize rapidly. The higher-temperature electrons transmit energy to the lattice through the electron-phonon scattering process, the electron-phonon coupling factor is used to govern the rate of electron-phonon thermal relaxation process. So far, the size effects of the electron-phonon coupling factor are still in controversial. We explore the femtosecond laser pump and probe method to study the nonequilibrium heat transfer in Au nano metal films, and explore the parabolic two-step radiation heating model to fit the experimental data. By studying on the different thicknesses of Au films′ electron-phonon coupling factors, we find that with the thin film thickness increases, the electron-phonon coupling factor decreases. The experimental data is in agreement with the theory model, which is based on the mean free path forwarded.