Abstract: In order to solve the problem of narrow working pressure range of microstructured flexible capacitive pressure sensors, a flexible “sandwich” structure capacitive pressure sensor based on expandable microsphere/polydimethylsiloxane (PDMS) dielectric layer was designed in this paper. Then the structure and morphology of the expandable microsphere/PDMS dielectric layer were characterized. The mechanical and electrical properties of the expandable microsphere/PDMS dielectric layer sensor based on expandable microsphere/PDMS dielectric layer were tested by self-built pressure and capacitance acquisition equipment. The results show that the Young’s modulus of the expandable microsphere/PDMS dielectric layer is significantly reduced due to the addition of expandable microsphere into PDMS, and the dielectric constant of the expandable microsphere/PDMS dielectric layer is increased under pressure. The working pressure range of the expandable microsphere/PDMS dielectric layer sensor is up to 400 kPa, and the maximum sensitivity reaches 0.06 kPa⁻¹. The expandable microsphere/PDMS dielectric layer sensor has good repeatability and stability under the load cycle of 100 kPa, and low hysteresis (4.7%). It can detect fingertip pressure accurately and rapidly, which has potential applications in areas of life and health.