Soft sensor is an important device of human-computer interaction for robot. This work proposes a method to fabricate multi-directional force flexible sensors with porous structure in a simple and economic way. The flexible electrode is fabricated by mixing carbon nanotubes / polydimethylsiloxane （CNTs / PDMS）， and the capacitive flexible multi-directional force sensor is assembled with porous silica gel as dielectric layer. The theoretical model of the flexible multi-directional force sensor is established and the performance parameters of the flexible sensor are obtained through experiments. The experimental results show that the theoretical model of the sensor agree well with the experimental curves. The dielectric layer with pore structure can improve the sensitivity of the sensor. The detection range of the sensor in the normal direction is 0~50 N and the resolution is 0.05 N. While the detection range in the tangential direction is 0~10 N and the resolution is 0.15 N. The sensor is integrated on an end-effector based on flexible pneumatic actuator for robotic fruit harvesting， and the holding and grasping force in the fruit grasping process is successfully detected. It further shows that the proposed sensor has good practicability.