The structural damage caused by micro-electro-mechanical system(MEMS) stress concentration in tunable vertical cavity surface emitting lasers(VCSEL) of GaAs-based and InP-based materials was studied. A bowknot MEMS cantilever structure was designed to reduce the von Mises stress at the fixed end of the cantilever and ensure the reliability of the device while ensuring the maximum displacement was invariable. The COMSOL software was used to optimize and analyze the influence of various parameters of the bowknot cantilever structure on the mechanical properties. The results show that the maximum von Mises stress at the fixed end of the optimized bowknot MEMS cantilever structure is reduced by 64% compared to the equal-section cantilever structure. The free spectral range of a bowknot MEMS wavelength-tunable VCSEL for GaAs-based materials is up to 45 nm.