The invention discloses a high-sensitivity optical MOS solid relay, which is characterized by comprising an input circuit, an optical isolator, a trigger circuit, a switch circuit and an output circuit; the input circuit comprises positive and negative feedback loops, and a capacitor discharge circuit is arranged on the output circuit; the input circuit comprises resistors R1, R2, R3, voltage regulator tubes D1, D2 and switching tubes T1, T2; the T1 and T2 form the positive feedback loop; an emitter of the T1 is connected with the R1 and is connected with an input end, a collector of the T1 s connected with a base electrode of the T2, and the base electrode of the T1 is connected with the collector of the T2 and is connected with the voltage regulator tube D2; the emitter of the T2 is connected with an isolation circuit; and R1 is connected with R3 in parallel, and R3 is connected with R2 in series. The high-sensitivity optical MOS solid relay disclosed by the invention can solve jitter, wrong trigger, proneness to radiation influence and other problems of the optical MOS solid relay, and has very high sensitivity.