The utility model relates to a temperature measuring circuit based on a linear optocoupler. The temperature measuring circuit based on the linear optocoupler comprises at least one temperature measuring passage. Each temperature measuring passage comprises one measuring electric bridge, a reference voltage generating circuit, an isolated power supply circuit, an operational amplification circuit, and a linear optocoupler module. The temperature measuring circuit based on the linear optocoupler uses a three-wire bridge type temperature measuring circuit, and the circuit is close to a PT100. The PT100 is accessed into a bridge arm through a conducting wire of an equal length, so that the resistance of the conducting wire can be eliminated. The reference voltage generating circuit provides a high precision voltage source for the electric bridge. When the impedance of the PT100 changes, the electric bridge balance is broken, a millivolt voltage is outputted, the corresponding impedance value is adjusted through a negative feedback proportion operational circuit, the millivolt voltage is converted into a desired value, and the voltage is outputted to a processor for operation processing after linear isolation. The temperature measuring circuit based on the linear optocoupler can be widely applied to the industrial temperature measuring field, and is very convenient to use.