A 760 nm single-mode， wavelength-tunable Vertical Cavity Surface-Emitting Laser （VCSEL） for oxygen sensing has been reported. The design method and device fabrication results of the 760 nm VCSEL have been reported in detail. By analyzing the gain characteristics of AlGaAs quantum wells， the composition and thickness of the quantum wells were determined， and the VCSEL structure with a gain peak and cavity mode mismatch of 10 nm at room temperature was designed. The single-mode power of the VCSEL exceeds 2 mW when the operating temperature is 25 °C， the side-mode suppression ratio （SMSR） is 28.1 dB， and the full angle of the divergence angle is 18.6°. As the operating current increases， the divergence angle of the VCSEL laser increases， but the far-field is still a circular and symmetrical spot with a Gaussian shape. By tuning the operating temperature and operating current of the VCSEL laser， the single-mode wavelength of the VCSEL can be continuously tuned from 758.740 nm to 764.200 nm. The current tuning coefficient of the laser wavelength changes from 1.120 nm/mA to 1.192 nm/mA， and the temperature tuning coefficient changes from 0.072 nm/℃ to 0.077 nm/℃ when the VCSEL operates at 15-35 °C. The SMSR of the VCSEL laser reaches 32.6 dB and 30.4 dB near the two characteristic absorption wavelengths of oxygen.