A novel method for the development of a highly sensitive triboelectric sensor based on porous PDMS matrix and carbon black (CB) particles is proposed. The porosity of the PDMS is controlled by using wet sugar particle sizes, and we fabricate a porous PDMS plate with a pore-to-volume ratio of 46%, which has a larger internal contact area compared to a non-pore one. To investigate the sensitive responses of the sensor, two key processes for the deposition of CB particles are conducted. One is the stirring process and another is ultrasonic vibration waving process. Based on the proposed method, a high-performance flat triboelectric sensor is fabricated. By a weight drop test of two different sensors, the amount of out-voltage is changed to approximately 29.1 and 95.1%, respectively. Through this study, we can evaluate that the sensitivity of triboelectric sensors is affected by the deposition method of the CB particles. The proposed flexible triboelectric sensor can be applied to analyze human physical behavior. Also, we believe that it can be applied to measure various physical signals such as contact force or gripping force with small values.