<p>The application of multi-material topology optimization affords greater design flexibility compared to traditional single-material methods. However, density-based topology optimization methods encounter three unique challenges when inertial loads become dominant: non-monotonous behavior of the objective function, possible unconstrained characterization of the optimal solution, and parasitic effects. Herein, an improved Guide-Weight approach is introduced, which effectively addresses the structural topology optimization problem when subjected to inertial loads. Smooth and fast convergence of the compliance is achieved by the approach, while also maintaining the effectiveness of the volume constraints. The rational approximation of material properties model and smooth design are utilized to guarantee clear boundaries of the final structure, facilitating its seamless integration into manufacturing processes. The framework provided by the alternating active-phase algorithm is employed to decompose the multi-material topological problem under inertial loading into a set of sub-problems. The optimization of multi-material under inertial loads is accomplished through the effective resolution of these sub-problems using the improved Guide-Weight method. The effectiveness of the proposed approach is demonstrated through numerical examples involving two-phase and multi-phase materials.</p>