In order to improve the sound pressure level(SPL) of piezoelectric micro-electro-mechanical systems(MEMS) speakers, a novel speaker diaphragm structure is proposed in this paper, The structure consists of four identical fan-ring driving units and a circular mass block in the middle, and the upper surface is covered with a layer of flexible material, forming a rigid-flexible-coupling sealed vibration membrane, The parameters such as radius r2 of the circular mass block and angle θ of adjacent fan rings were optimized, It was found that the maximum SPL was obtained when θ=50° and r2 =700 μm, The sound pressure level of the novel structure proposed in this paper is 5 dB higher than that of the optimized clamped circular multilayer diaphragm under the condition that the diaphragm area is the same and the resonant frequency is basically the same,