Cyclopropenone is an organic compound consisting of a cyclopropene framework with a ketone functional group. It has been found in various natural compounds. Cyclopropenone can also undergo different reactions, and photo-decarbonylation is one of the most unique. It is clean and one of the fast photo reactions. In this dissertation, we focused on mechanistic study and application of the photo-decarbonylation of cyclopropenone derivatives. Although photodecarbonylation is the one of the most common reaction of cyclopropenones, there is very little agreement in the literature on the photoactivation mechanism. We discussed some finding we had recently on the mechanism of photo-decarbonylation reaction both in nanosuspension and in solution. In ultrafast transient absorption spectroscopy, with the help of collaborator, we proposed different mechanism for photo-decarbonylation of photo-ODIBO under 321 nm and 350 nm. In addition, we reported our latest findings on the different photo reaction quantum yield of decarbonylation in basic condition and in acidic conditions. We used fluorescent spectroscopy to study fluorescent quantum yield of solution in both conditions to explain those differences. Those findings pave ways for determination of the mechanism of the photo-decarbonylation We also discussed some synthetic work based on using carbonyl groups incyclopropenone as photo-labile protecting groups. With different functional groups, we achieved different linkages between SPPAC moieties, such as ODIBO or ADIBO and biomacromolecules. We hope those methods would provide with new insight of SPAAC reagents in biolabeling.