自由电子激光(FEL)光源对化学、生物、材料等领域中微观电子结构的研究有着不可替代的优势。FEL光源可以在10 fs的时间尺度内发出超短脉冲，因此其最重要的应用之一就是研究微观结构内部的超快动力学(飞秒泵浦-探测)。快速发展的自由电子激光实验技术在不同研究领域均获得广泛的应用。文章主要介绍近年来自由电子激光在光化学领域中的应用。未来在上海建成的硬X射线自由电子激光项目，可支撑物理、化学、材料、环境和生物科学等多学科及交叉科研领域，做出重大的科研成果。

The experimental technology using X-ray free electron laser source (XFEL) has irreplaceable advantages in the research direction of microstructure and electronic structure in the fields of chemistry, biology, materials and other fields. Free electron laser (FEL) sources can emit ultrashort X-ray pulses with pulse durations of 10 fs, making conventional optical lasers ideal for pump-probe experiments. One of its most important applications is the study of ultrafast dynamics inside microstructures (femtosecond pumpprobe measurement). It is a typical technology for studying ultrafast dynamics at very small scales. The rapid developmenting ultrafast X-ray spectroscopy experimental technology has been widely used in different research fields. This article mainly introduces the application and technological development of femtosecond X-ray free electron lasers in the field of photochemistry in recent years. In the future, with the completion of the hard X-ray free electron laser in Shanghai, it can support multi-disciplinary and interdisciplinary fields such as physics, chemistry, energy, materials, environment, etc., and make significant scientific research achievements.