The invention relates to a wearable flexible stress sensor and a preparation method and application thereof. Firstly, functional ink suitable for screen printing is prepared, and is printed on a wearable substrate through a screen printing method, and the stress sensor of a desired specification is produced. The stress sensor is used for monitoring physical deformation of stretching, bending, touching and the like from small ranges to large ranges, and has multiple application in the electronic skin fields and the biomedical application fields of human skins, expressions, pulses, heartbeats and the like, the human-computer interaction fields and the fields of virtual reality, entertainment technology and the like. The flexible stress sensor of the invention has the following advantages that the sensor has excellent stretching elasticity, and stretching strain can reach 100%; sensitivity is extremely high, and a sensitivity parameter (Gauge Factor) can be up to 8000 or more; linear relationships of working curves are excellent, stretching repeatability is good, and a stretching cycle lag is small; and a preparation process is simple, costs are low, massive integrated-device preparation is suitable, and application prospects are wide.