During the past few years,regulation and controlling of the two-dimension(2D) self-assembled supramolecular structure on surface have drawn increasing attention in nanoscience and technology.External stimuli have been widely used to regulate these 2D nanostructures.Among various external stimuli approaches,photo-regulation as one of the most outstanding means of regulation has been extensively studied because different wave bands can lead to molecular conformation variation and new bonds to gain new molecules.In this review,the photo-regulated self-assembled structure on solid surface as well as the photo-reactions of different molecules substituted with photo-sensitive groups are introduced to give us an insight into on-surface photochemistry,which plays an important role on the nano-devices fabrication.Notably,these photo-sensitive behaviors as well as the formed structures on surface were probed at sub-molecule level by unique scanning tunneling microscopy(STM) technique. During the past few years, regulation and controlling of the two-dimension (2D) self-assembled supramolecular structure on surface have drawn increasing attention in nanoscience and technology. Externally stimuli have been widely used to regulate these 2D nanostructures. All kinds of external stimuli approaches , photo-regulation as one of the most outstanding means of regulation has been extensively studied because different wave bands can lead to molecular conformation variation and new bonds to gain new molecules. In this review, the photo-regulated self-assembled structure on solid surface. as well as the photo-reactions of different molecules substituted with photo-sensitive groups are introduced to give us an insight into on-surface photochemistry, which plays an important role on the nano-devices fabrication. Notably, these photo-sensitive behaviors as well as the formed structures on surface were probed at sub-molecule level by unique scanning tunneling microscopy (STM) technique.