介绍了扫描电子显微镜 (SEM)的基本工作原理 ,着重分析了在 SEM初始电子束作用下 ,各种成像信号产生的方式及其特点 ,确定二次电子信号因成像分辨率高、携带成像信息丰富而成为 SEM的最终信号源。针对此信号在实际应用中暴露出的缺陷 ,介绍了解决办法 ,从而使 SEM的成像性能得以大幅提高 ,使用范围大为扩展 The basic working principle of scanning electron microscope (SEM) is introduced. The way of generating imaging signals and their characteristics under the action of SEM initial electron beam are emphatically analyzed. It is confirmed that the secondary electron signals have high imaging resolution and rich imaging information And become the ultimate signal source of SEM. In view of the defects exposed by the signal in practical application, the solution is introduced, so that the imaging performance of the SEM can be greatly improved and the use range is greatly expanded