In this paper, a numerical algorithm with space-time second-order accuracy is constructed for a fourth-order nonlinear time fractional hyperbolic equation. Firstly, a low order parameter β =α-1 is introduced to reduce the Caputo fractional derivative ofα ∈ 1, 2 to the Caputo fractional derivative of β ∈ 0, 1 . Secondly, two auxiliary variables v=ut , ζ=Δu are introduced to transform. the fourth-order nonlinear time fractional hyperbolic equation into a low-order nonlinear coupled system with integral term. The fractional derivative term is discretized in the time direction by L2-1σ formula, and the integral term is discretized by the complex trapezoidal formula. Using the traditional Galerkin finite element method in space, the fully discrete finite element scheme of the low-order nonlinear coupling system is obtained. Taking the uniform. rectangular division on a two-dimensional region as an example, the specific forms of stiffness matrix and load matrix are given by the bilinear basis function, and the detailed algorithm implementation process of the fully discrete numerical scheme is obtained. Finally, numerical simulations are carried out for one-dimensional and two-dimensional examples. Compared with the original equation, the low-order system can observe the changes of three unknown variables u, v, ζ at the same time, and the errors, images and convergence orders of the three unknown variables are listed in detail under different parameters and different space-time steps, which fully verifies the feasibility and effectiveness of the algorithm.