The invention relates to a capacitive flexible pressure sensor based on microstructural dielectric layers and a preparation method of the capacitive flexible pressure sensor and belongs to the technical field of sensors. The capacitive flexible pressure sensor comprises an upper flexible substrate, a lower flexible substrate, an upper conducting layer and a lower conducting layer, wherein the upper conducting layer is attached to the inner surface of the upper flexible substrate, the lower conducting layer is attached to the inner surface of the lower flexible substrate, and the microstructural dielectric layers are arranged between the upper conducting layer and the lower conducting layer. Compared with the prior art, different microstructural dielectric layers are designed for the capacitive flexible pressure sensor, the sensor performance can be effectively regulated according to change of conditions such as shape, size, distribution and the like of each dielectric layer microstructure, and preparation of the capacitive flexible pressure sensors with different sensitivity and test ranges is realized. Besides, the microstructures prepared with methods such as microcapsule foaming, impressing, replica transfer, 3D printing and the like are low in cost, high in efficiency, low in energy consumption and particularly suitable for large-area and large-scale production, and application and popularization of the sensor are facilitated.