The multiphoton ionization of the hydrogen-bonding cluster pyridazine-methanol (C 4 H 4 N 2 -CH 3 OH) was studied using a time-of-flight mass spectrometer at the wavelengths of 355 and 532 nm. At both wavelengths, a series of protonated C 4 H 4 N 2 -(CH 3 OH) n -H + cluster ions were obtained. Relevant ab initio calculations were performed with HF and B3LYP methods. Equilibrium geometries of both neutral and ionic C 4 H 4 N 2 -CH 3 OH clusters, and dissociation channels and dissociation energies of ionic clusters, are presented. The results show that when C 4 H 4 N 2 -CH 3 OH is vertically ionized, C 4 H 4 N 2 H + and CH 3 O are the dominant products via proton transfer reaction. A high energy barrier makes another channel corresponding to the production of C 4 H 4 N 2 H + and CH 2 OH disfavored.