In order to realize the application of fiber grating sensor in wearable system, a wearable fiber grating sensor demodulation system based on silicon-based photonic integrated chip was proposed. The photonic integrated chip based on Belgium iSiPP50G process was composed of 4×1 long wavelength VCSEL array, 1×8 array waveguide grating, 2×2 MMI coupler, 4×1 fiber grating coupler array, GE-on-SI waveguide photodetector, straight waveguide and curved waveguide, etc. After completing the gold wire bonding of the VCSEL light source and the optical fiber coupling package of the photonic integrated chip, a wristband demodulation circuit was designed to measure the human body temperature and heart sound signals in real time. The experimental results show that the dynamic wavelength detection range of the demodulation system is 1 540 nm~1 560 nm, the wavelength resolution is 0.08 pm, the demodulation accuracy is 5 pm, the temperature monitoring range is 35 ℃~42 ℃, and the error is ±0.1 ℃. It can detect the heart sound signal in the frequency range of 50 Hz~100 Hz, identify the first heart sound and the second heart sound, and calculate the cardiac cycle, heart rate, the first heart sound time limit, the second heart sound time limit and cardiac parameters.