双光栅衍射场的干涉效应既具有理论研究价值又具有很实际的应用价值.本文利用波前相因子分析法，推导出了双余弦光栅夫琅禾费衍射场的理论结果;分析了当两个光栅在横向有相对运动时，各级衍射斑光强的变化规律.通过实验观测映证了光强变化与数值计算结果是一致的.这一理论结果是双光栅衍射类实验设计的基础，而这类实验可以用于测量微小振动的振幅和频率.

The effect of interference of diffraction by a double grating is worthy to study theoretically and provides possibilities of application. We calculate the pattern of Fraunhofer diffraction by a cosine-style double grating with a wavefront phase-factors method. Some formulas about intensities of each order diffraction are deduced as one grating translates along another. Some experiment results are shown to coincide with the diffraction patterns by numerical simulation. These formulas form a foundation for experimental applications. One of these obvious applications is to measure the amplitude and the frequency of a micro-vibration.