采用蒙特卡罗理论模拟加速电子在氮铝镓晶体薄膜中的运动轨迹，研究加速电压与高能电子所能达到样品深度的数学关系，并通过紫外可见光透射法获得晶体薄膜的光学厚度。根据理论模拟结果，选择合适于本样品的加速电压、电流与电子束直径等实验条件，电子探针波谱法测定AlxGa1-xN薄膜中铝元素含量，由两个电子探针实验室进行分析，每个实验室测量6个样品，共12个样品。从重复性测量、X射线强度、物理参数、校准用标准物质及仪器检测限等因素，对电子探针波谱法测量AlxGa1-xN薄膜材料中铝含量的测量不确定度进行分析。研究结果表明电子探针波谱法测量AlxGa1-xN晶体薄膜组分（x=0.8）的相对测量不确定度为2.7×10-2，包含因子k=2。

The motion tracks of high energy accelerated electron in AlxGa1-xN crystal film material are simulated by Monte Carlo method, The relationships between accelerated voltages and the depths which kV voltages accelerated electron can reach are studied. The experimental thickness of crystal film epitaxial layer is measured by ultraviolet visible light transmittance spectra method. The aluminium composition of crystal film epitaxial layer is determined by electron probe microanalysis/wavelength dispersive spectrometer (EPMA/WDS) method, with suitable experimental parameters of accelerated voltage and current and beam diameter from theoretical simulation. The experiment is carried out between two EPMA laboratories, six samples by each laboratory. The source of measurement uncertainty is analyzed including measurement reproducibility and X-ray intensity and physical parameter etc.. The experimental results show that the measurement uncertainty of EPMA/WDS for the determination of aluminium composition (x=0.8) is 2.7×10-2, the coverage factor k is 2.