The invention belongs to the technical field of biosensors, in particular to a fully automatic high-throughput optical biosensing device. The device includes: oblique incident light reflection difference imaging unit, sample and liquid processing unit, system control and data acquisition and processing unit. Oblique incident light reflection difference imaging unit includes monochromatic light generator, beam expander, polarizer, polarization modulator, phase shifter, lens, mechanical translation stage, imaging lens, analyzer and photodetector; sample and liquid The processing unit includes a biological chip, a fluid chamber, a buffer solution pump, a sample solution pump, a selection valve and a switching valve; the system control and data acquisition processing unit includes an amplification circuit, an AC weak signal detector and an electronic computer. The device can perform high-throughput, in-situ, real-time and rapid detection of biochips, fully automatic operation, and high detection efficiency. It has a wide range of applications in life science research, high-throughput drug screening, clinical diagnosis, food and environmental safety testing application prospects.