A plantar pressure sensing system is located at a sole of shoe. The plantar pressure sensing system includes a first layer, a second layer a plurality of sensor, a plurality of convex portions, a plurality of connection portions, a processor and a storage. The processor is coupled with the storage and configured to be connected with the plurality of sensors. The plurality of sensors are configured to form the first layer. The plurality of convex portions and the plurality of connection portions are configured to form the second layer. Overall, the plantar pressure sensing system is able to detect pressure with the sensors by setting the alignment of the convex portions, thereby obtaining a more accurate pressure(s) reading from the sole of shoe. The data validity of the plantar pressure sensing system is improved.