Acetonitrile-solvated Mg+ complexes Mg+(NCCH3)n were produced in a pick-up source. The Mg+(NCCH3)n clusters were subjected to photodissociation in a time-of-flight reflectron mass spectrometer. Except for a minor reactive product Mg1-NC at short wavelengths, only nonreactive (or evaporation) fragments were observed from photodissociation of Mg1 (NCCH3) n (n=1-4). Action spectra of Mg+(NCCH3)n (n=1-4) were recorded in the spectral region of 230-560nm, which provide insight into the structure and photodissociation dynamics of the complexes. For all the complexes we studied, the ligands are believed to be in the first solvation shell. Both the evaporation and reaction processes occur on the ground state surfaces of the complexes. By using the DFT/B3LYP and CIS methods, the most stable ground-state structures and the excitation spectra for Mg+(NCCH3) 1-3 were obtained. The ab initio predictions appear to be consistent with the experimental results.