In order to solve the transverse vibration problem of two?span continuously modified Timoshenko beam on viscoelastic four?parameter foundation， a new vibration governing equation is established by combining two?span continuously modified Ti? moshenko beam with viscoelastic four?parameter foundation. By using the echo matrix method， bisection and golden section meth? od， the relation and difference between the natural vibration characteristics of two?span （equal?span， unequal?span） continuously modified Timoshenko beam and single?span modified Timoshenko beam on viscoelastic four?parameter foundation are analyzed. The results show that for the modified Timoshenko beam on the viscoelastic four?parameter foundation， the natural frequency of each order of the single?span beam is less than that of the two?span continuous beam， the even?order natural frequency and attenua? tion coefficient of the single?span beam are the same as the odd?order natural frequency and attenuation coefficient of the two equal?span continuous beam， and the odd?order natural frequency of the unequal?span two?span continuous beam is less than that of the two?span continuous beam. The even?order mode shapes of two equal?span continuous modified Timoshenko beams are sym? metrical with respect to the supports in the middle of the span， and the odd?order modes are antisymmetric with respect to the mid?span.