在传热学基础上建立了涂层的三维瞬态导热模型，利用ANSYS仿真软件对施加有正弦规律变化热流密度的涂层试件进行有限元分析；运用两次加载、减法处理的方法有效克服了常量和环境因素带来的影响，然后讨论了数据拟合求相位的方法；改变加载频率，得到了多组涂层厚度与相位的定量关系曲线，从理论计算的角度揭示涂层厚度和相位及加载频率的定量关系；最后利用曲线中的线性线段，总结确定了涂层厚度与相位的定量关系，为利用锁相法对涂层厚度进行精确测量提供了理论依据。

On the basis of the heat transfer, a three-dimensional heat conduction model was proposed. The coating applied sinusoidal variation of heat flux was analyzed using large-scale finite element analysis software ANSYS. The use of two loading and subtraction effectively overcome the effects brought about by the constant part and environmental factors. Then data fitting method for seeking phase was discussed. Changing loading frequency, multiple sets of the quantitative relationship curves were obtained. From the theoretical point of view, the relationship of the phase between the modulation frequency and thickness were revealed. Finally, using the linear stages in curves, the quantitative relationship between phase and thickness was identified. A theoretical basis for precise measurements of coating thickness using infrared lock-in method was provided.