In engineering projects， we often have to deal with dynamic analysis of large beam-type structures such as launch vehicles， train cars and high-rise buildings. As the computational workload is very large， model reduction is usually essential. In order to solve this problem， a multi-point cohesion method for beam-type solid structures is proposed. Based on the plane section assumption of beam theory， the displacements of FEM nodes on each cross section are approximated by the motion of cohesion points of the cross section through a displacement transformation matrix， resulting in the localized base vectors which will be used for model reduction. The method can also be applied to simulation of liquid propellant launch vehicles. The solid reduction method is then further proposed. Utilizing the characteristics that the liquid is incompressible and can’t withstand shear stress， the elastic modulus and Poisson’s ratio of the solid elements used to establish the liquid propellant are reasonably defined. Then the simplified model can be obtained by the multi-point cohesion method. Results of illustrative examples indicate that， the simplified model derived by the multi-point cohesion method can not only improve computation efficiency， but also ensure that the relative error of the results is less than eight percent. In the meanwhile， the results confirm effectiveness of the model reduction method.