[Aim]  Oviposition is a crucial aspect of insect behavior, and observing oviposition behavior can provide fundamental data for further exploration of pest control and the conservation of beneficial insects. [Methods]  An industrial CCD video microscope paired with an infrared light source were used to record the oviposition behavior of Monolepta signata in a custom-built insect oviposition chamber. Additionally, different substates were used to assess the oviposition preference of M. signata. [Results]  The highest oviposition rate was observed when white sand was used as a substrate. The oviposition process of M. signata on white sand was categorized into six stages: Host approach, contact probing, probing identification, oviposition, retrieving the ovipositor, and stationary. The probing identification stage was the longest, with females using the end of their abdomen to probe and identify oviposition sites. A positive correlation was observed between the angle of the female abdomen and the substrate surface, and the depth of oviposition and the length of the abdominal tip during oviposition. [Conclusion]  The combination of a CCD video microscope, infrared light source, and a custom-built oviposition observation chamber enabled clear observation of the oviposition process of M. signata in the soil. This study introduces a novel approach for observing insect oviposition behavior, furthering the investigation of their biological traits for practical applications. It also offers technical support for the control of phytophagous insects that oviposit in the soil.