Photodissociation spectrum of MgCH3I+ is measured by using a reflectron time-of-flight mass spectrometer and a tunable UV laser. There are three bands peaking at about 27 200, 29 600, and 38100 cm(-1), which all originate from P-2 <-- S-2 transition of Mg+. In the dissociation processes, five kinds of ions, CH3+, Mg+, I+, CH3I+, and MgI+, are observed as fragments. Photodissociation spectrum is assigned by theoretical calculations, and dissociation processes are discussed from the consideration of potential energy curves including charge transfer states along the Mg-I bond distance obtained by CIS calculation. (C) 2003 Elsevier B.V. All rights reserved.