Intramolecularly bridged diarylethenes exhibit improved photocyclization quantum yields because the anti-syn isomerization that originally suppresses photocyclization in classical diarylethenes is blocked. Experimentally, three possible channels have been proposed to interpret experimental observation, but many details of photochromic mechanism remain ambiguous. In this work we have employed a series of electronic structure methods (OM2/MRCI, DFT, TDDFT, RI-CC2, DFT/MRCI, and CASPT2) to comprehensively study excited state properties, photocyclization, and photoreversion dynamics of 1,2-dicyano [2,2]metacyclophan-1-ene. On the basis of optimized stationary points and minimum-energy conical intersections, we have refined experimentally proposed photochromic mechanism. Only an S-1/S-0 minimum-energy conical intersection is located; thus, we can exclude the third channel experimentally proposed. In addition, we find that both photocyclization and photoreversion processes use the same S-1/S-0 conical intersection to decay the S-1 system to the So state, so we can unify the remaining two channels into one. These new insights are verified by our OM2/MRCI nonadiabatic dynamics simulations. The S-1 excited-state lifetimes of photocyclization and photoreversion are estimated to be 349 and 453 fs, respectively, which are close to experimentally measured values: 240 +/- 60 and 250 fs in acetonitrile solution. The present study not only interprets experimental observations and refines previously proposed mechanism but also provides new physical insights that are valuable for future experiments.