以一种新方法建立了俯仰激励下圆柱贮箱类液固耦合系统的动力学方程。对液体子系统和结构子系统分别得到压力体积分形式的 L agrange函数和标准形式 L agrange函数 (动能减去势能 ) ,由变分方程和 L agrange方程可以建立系统的动力学方程。通过数值仿真发现 ,在一定的激励幅值和频率下 ,该耦合系统会出现零点漂移、分叉等非线性动力学现象 A new method is used to establish the dynamic equation of liquid-solid coupling system of cylindrical tank under pitch excitation. The L agrange function and the standard form L agrange function (kinetic energy minus potential energy) of pressure subsystems are obtained respectively for liquid subsystems and structural subsystems, and the system dynamic equations can be established by variational equations and L agrange equations. Through numerical simulation, it is found that under certain excitation amplitude and frequency, the coupling system will appear zero drift, bifurcation and other nonlinear dynamic phenomena