In　this　article,　the　hetero-intermolecular　[2+2]　photocycloaddition　of　1,4-dihydropyridines　(1,4-DHPs)　in　solution　was　reported,　wherein　head-to-tail　(HT)　dimeric　products　(syn-dimers　and　cage　dimers)　were　formed　exclusively　through　successive　inter-　and　intra-molecular　[2+2]　cycloaddition.　The　effects　of　irradiation　wavelength,　solvents　and　substituents　on　the　efficiency　of　these　transformations　were　investigated.　To　shed　light　on　the　intrinsic　characteristics　and　stereoselectivity　of　the　photocycloaddition,　DFT　and　TDDFT　theoretical　calculations　were　carried　out　to　reveal　detailed　reaction　processes.