In recent years, with the widespread application of laser processing technology in micro-nano scale materials and devices, research into characterization techniques for laser processing has played a crucial role in understanding laser-material interactions, optimizing the processing process, and improving processing quality. These techniques have found broad applications in fields such as micro-nano optoelectronic device fabrication and biomedical material processing. However, as processing precision improves and application areas expand, performing in-situ rapid and real-time characterization of laser-processed micro-nano structures has become a key technical challenge. We introduce the major in-situ characterization techniques currently used in laser micro-nano processing, classifying them into two categories: geometric in-situ characterization and ultra-high spatiotemporal resolution in-situ characterization. Geometric in-situ characterization, including techniques such as scanning electron microscopy (SEM) and structured light three-dimensional imaging, is widely employed for high-resolution imaging of surface morphology, enabling rapid in-situ characterization of laser-processed micro-nano structures. Ultra-high spatiotemporal resolution in-situ characterization techniques, such as pump?probe imaging and single-pulse ultrafast imaging, allow observation of the transient evolution of materials during laser processing with picosecond to femtosecond temporal resolution. These techniques reveal changes in microstructure and material properties, providing crucial insights into the interaction between lasers and materials. Finally, we summarize the findings and present an outlook on the future development of in-situ characterization technologies for laser processing.