A tunable mechanism has been investigated to control the photo-release behavior of phototrigger compound (KP-OAc) by Multi-configurational ab initio calculations. The photo-transformations of KP-OAc in the basic and acidic forms are triggered by the photoexcitation at 323 and 252 nm, respectively. The former one can produce the carbanion intermediate followed by the release of AcO- group induced by the efficient charge delocalization of carbanion moiety. While the photorelease channel is switched off in the latter case, for only the triplet biradical intermediate could be yielded when the decarboxylation is driven by the water aided excited-state intramolecular proton transfer (ESIPT).