Abstract: A high-voltage linear optocoupler is designed, which could transmit analog signals accurately and meet the requirement of high-voltage isolating. It contains a GaAlAs infrared emitting diode optically coupled to a Si-PIN photodiode. The operation principle and the design of circuit are described. The main factors affecting the isolating properties and linearity are analyzed. Measuring results indicate that the device possesses an excellent isolation properties and high linearity.