Flexible capacitive pressure sensors with simple structure and low power consumption have attracted great interest because of their promising applications in wearable electronics. However, assembling a pressure sensor with high sensitivity, low detection limit, and wide dynamic range is still a big challenge. Here, a sandwich-like, flexible capacitive pressure sensor is reported with micropyramid array electrode and porous dielectric layer. Under external stimulus pressure, the distance between two electrodes, and dielectric constant of dielectric layer will change simultaneously, resulting in high sensitivity (2.51 kPa) of the sensor. Due to the micropyramid array electrode, the sensor exhibits low detection limit (2.0 Pa), fast response speed (84 ms), wide working range (>10 kPa), and high stability (>5000 dynamic cycles). Finite-element analysis also reveals that the larger duty ratio and altitude of micropyramid arrays lead to higher sensor sensitivity. By depicting the deformation of micropyramid during compression, the sensing mechanism of these sensors is discovered, providing a potential direction for developing sensitivity and linear range. Additionally, the sensor has been demonstrated to be efficient in monitoring human motion, such as muscle activation and rope skipping, showing high potential in the field of sport wearable equipment.