As an important component of wearable devices, the key parameters of the blood oxygen sensor (detection efficiency, uniformity, etc.) directly affect the performance indicators of the device. Based on the TracePro simulation platform, the simulation design of blood oxygen sensor is carried out to optimize the light propagation signal. A multilayer skin tissue model conforming to Beer-Lambert's law and Henyey-Greenstein scattering function is constructed to explore the propagation law and difference of light in various skin tissues under the influence of absorption and scattering. For the blood oxygen sensor module, the spectrum and spatial light distribution of the light source and the spectral-angular response characteristics of the detector are simulated. Multi-channel module design is carried out, and the design of detector space layout, detection distance, center distance, light window, and anti-spurious light structure are optimized with luminous flux and illumination uniformity as evaluation indicators. The surfaces of constant-angle and variable-angle Fresnel lenses are constructed, the influences of surface parameters for Fresnel lenses on the spatial light distribution are compared, and the optical signal transmission before and after optimization is compared by the variable-angle Fresnel lens optimization module. Results show that the detection efficiency is increased by up to ~27% and the illumination uniformity is increased to 94.45% after optimization.