Intracluster ion-molecule reactions of dimer cations of various phenylsilanes were investigated in order to elucidate reaction mechanisms of phenylsilane cation reported in the gas-phase FT-ICR study. Two types of reactions, SiR3 elimination and SiR2+: transfer, were observed. In the latter case, our observation strongly supported that a precursor of the reaction has a pi-type complex configuration, [C6H6. SiR2](+), which has been proposed before. On the contrary, in the former case, a dimer cation forms a reaction intermediate and then it dissociates preferentially to a larger exothermic channel.