Stretchable strain sensors play an increasingly important role in artificial intelligent devices. However, high-performance strain sensors have been slowly developed owing to the harsh requirement of self-powered function, long cycle life and high resolution. Here, we report a self-powered stretchable graphene-ecoflex composite strain sensor based on photo-thermoelectric (PTE) effect induced electricity. The device exhibits a high strain sensitivity of -0.056 ln(nA)/% with strains ranged from 0% to 20% under 980 nm light illumination, where the strain sensitivity can be found to increase with increasing light intensity. The strain sensor maintains outstanding dynamic stability under periodic strains ranged from 0 to 100% in 100 cycles. The sensing resolution can be as high as 0.5% with both the response and recovery time of less than 0.6 s. It can precisely monitor human joint motions and stretchable strains by implanting the device in pork. Open image in new window