Graphical abstractDisplay Omitted Highlights? A flexible capacitive sensor was developed for plantar pressure measurement. ? PDMS material was used for the dielectric layer of the sensor. ? The stiffness of PDMS was investigated under different mixing ratios. ? The sensor can measure the pressure up to 945KPa. A flexible capacitive pressure sensor has been developed for plantar pressure measurement in biomechanical application. Polydimethylsiloxane (PDMS) material was selected as the material of the dielectric layer because of its advantages of high dielectric constant and tunable elasticity. In this work, PDMS characterization was conducted to investigate the stiffness under different mixing ratios of PDMS pre-polymer and the curing agent. PDMS in 16:1 mixing ratio was selected since it has the most linear stress-strain relationship with the highest elasticity within our pressure region of interest. Since the sensor was designed for the measurement of the plantar pressure, it can measure the pressure up to 945kPa. Moreover, flexible printed circuit film was utilized as the sensor substrate for the minimum disturbance of the measurement to the curved surface and reservation of the electronic circuit integration. Because of the miniaturization and flexibility of the sensor, it has the potential to develop shoe-integrated sensor system for long-distance data collection for gait analysis.