In this study, the diamond-like carbon (DLC) coating was deposited on magnalium diaphragm by pulsed plasma enhanced chemical vapor deposition technology. The morphology and composition of the DLC coating deposited by different processes were characterized by SEM, RAMAN and AFM, and the mechanical properties of magnalium diaphragm with DLC coating were studied. Compared with magnalium diaphragm, the DLC coating improved the surface roughness, hardness and elasticity modulus. The frequency response curve and harmonic distortion showed that the DLC coating increased the upper limit of frequency response and imparts high fidelity to the loudspeaker. Audio equipment fabricated with magnalium diaphragm with DLC coating had good timbre naturalness, sound field expression, vocal performance and overall evaluation, which can effectively improve the human subjective listening effect.