The random vibration of coupled vehicle-bridge system under moving vehicular loads is studied. The bridge and vehicle are modeled as a continuous beam with elastic bearing and a two-DOF system with linear suspensions and tire flexibility respectively. The power spectral density of bridges surface irregularity is taken as input. Modes of continuous beams are obtained by transfer matrix method. According to state space theory and general evolutionary random processes, the method of analyzing random response of coupled system is derived. The effects of types of mid-support, bending stiffness, location of elastic bearing, vehicle velocity，and bridge surface roughness on the random response of coupled vehicle-bridge system are discussed.