Abstract: The paper proposed a design scheme of an intelligent type electronic over-load protection relay of motor based on μC/OS-II embedded operating system and LPC2292 embedded microprocessor.On the basis of adopting symmetrical component method to analyze common faults of three-phase asynchronous motor,the paper introduced hardware design of the relay and introduced priority distribution of all kinds of tasks of μC/OS-II embedded operating system and design thought of the data communication part based on CAN bus in details.The relay can select the best matching mode to control and protect motor automatically according to running state of load as well as intercommunicate with upper computer.The experiment running and field application results showed that the relay has easy operation,reliable performance,perfect protection functions and strong anti-interference ability.