The mechanism of chemiluminescent decomposition in Spiro Acridyl Substituted Adamantylidene 1,2 Dioxetane (SAAD) is explored by LC wPBE /6 31+G* method using the Gaussian 09 software. The energetics of the d ecomposition reaction via transition states/intermediates at the lowest singlet and triplet states are studied using complete optimisation as well as frequency analysis. According to the findings of the current study, SAAD's chemiluminescent decompositio n occurs via a biradical pathway that includes the production of the triplet biradical intermediate 3 BR. The findings are in accordance with earlier theoretical and experimental studies.