The invention relates to a method and device for observing and controlling a rotor position in motor control. According to the method and the device, an initial position angle of a motor rotor can be observed; angular errors caused by an imprecise assembled angle of a Hall sensor can be eliminated by online discrimination of software; a real-time speed detection program is provided to eliminate an angular accumulated error caused by imprecision of an angular speed omega; a rotor position angle can be precisely tracked in a motor vector control operation process, the rotor angle is prevented form overflowing, and self-detection of the motor in reverse rotation can be realized; and when a certain sensor has a fault, a system can judge a fault point per se and performs self-adaption to achieve the function of still normally running. According to the device and the method, independence on a hardware circuit is reduced, observation and real-time tracking of the rotor position angle can be realized, the function of fault judgment of the system can be used for protecting the motor, and loss caused by motor locking or running out is prevented. The device has a great practical value in the fields of electric vehicles and precise machine tools, and has the advantages of reliability in operation, low cost and wide application range.