Multiscale structures can be more robust to partial damage than solid structures. Inspired by this, in this paper, a fail-safe topology optimization method is proposed for multiscale structures. Computational cost is reduced by simplifying the partial damage of the truss-like microstructure and a sextic polynomial function is used to fit the effective elasticity tensor obtained via the homogenization method. The Heaviside projection is applied to optimize the fail-safe multiscale topology, resulting in designs that are clearer and more robust. Three numerical examples are tested to demonstrate the advantages of the optimized multiscale structures. By choosing appropriate microstructure configurations, optimized multiscale structures can exhibit greater resistance to failure and improved comprehensive performance compared to optimized solid structures. Additionally, numerous self-supporting microstructures of multiscale structures make them easier to manufacture using additive processes.