Abstract: Compared to transmission electron microscopy (TEM), scanning electron microscopy (SEM) has the advantages of batch sample loading, lower cost, and three-dimensional imaging. However, during the SEM imaging of small-sized nanoparticles, several technical problems, including easy carbon deposition, insufficient resolution, and weak information on morphological structure, restrict the applications. Taking ultra-small sized hollow (34.4 nm) and solid (13.3 nm) Ni₂P nanoparticles as the example, this article focuses on exploring how to obtain SEM images with high resolution and clear morphology by adjusting parameters such as operating mode, working distance, acceleration voltage, and beam current. The results show that the resolution of secondary electron (SE) images obtained by Optiplan-T2 and Immersion-T3 modes are significantly better than that of the ETD probe in standard mode. Additionally, the SE images have abundant surface morphology information and good three-dimensional sense. This is because the T3 probe is positioned the highest and only collects high-altitude secondary electron signals, which enter the lens at a more collimated angle and with lower energy. Therefore, the Immersion-T3 probe produces SE images with the highest resolution, signal-to-noise ratio, and good morphological contrast, but the internal structure of the particles is almost invisible. In the Optiplan and Immersion mode, the T1 probe produces BSE (backscattered electron) images with good composition contrast. Although the depth of field is smaller, it is most advantageous for observing hollow structures. The study also found that if the working distance is too small, the SE images have good resolution but poor depth of field. Conversely, if the working distance is too large, the SE image resolution is slightly weaker, but the depth of field is better. Based on the measurement results of image quality, for the Ni₂P nanoparticles, selecting an appropriate working distance (~8 mm) can obtain high-quality SE images. Increasing the acceleration voltage can effectively improve the image resolution (for hollow Ni₂P, it can reach 2.3 nm at 30 kV). The signal-to-noise ratio will increase with the increase of beam current. But if it is too large, the particle edges will get blurring. Therefore, selecting the appropriate beam current (~0.2nA) can obtain a better imaging effect. The above research results provide a reference for selecting SEM imaging for small-sized and hollow structured nanoparticles.