With the advances in artificial intelligence and communication technologies, flexible microwave magnetic materials have become essential for flexible microwave detectors, wearable microwave sensors, and flexible spintronics. Here, a highly stable in-plane (IP) ferromagnetic resonance (FMR) and a tunable out-of-plane (OOP) FMR character are demonstrated in the flexible microwave magnetic Li0.35Zn0.3Fe2.35O4 (LZFO) (111) epitaxial thin films under external mechanical bending. Both the IP FMR line width and resonance field ( Hr) are basically unchanged when the sample was bent under an external tensile or compressive bending strain and deformation. However, the OOP FMR spectra (including Hr and absorption peak) could be tuned by mechanical bending, i.e., the LZFO sample possesses two OOP FMR absorption peaks at an external bending curvature. Meanwhile, excellent mechanical antifatigue and mechanical retention characteristics have also been obtained in the LZFO sample. The highly stable IP and the tunable OOP FMR spectra in the same LZFO sample with excellent mechanical antifatigue character have a promising prospect in microwave magnetic devices and flexible spintronics.