The invention discloses a motor rotor position detection method and device and belongs to the technical field of driving control. The method is used for a motor control main chip and comprises the steps of: receiving output signals of a rotary transformer, wherein the output signals are excited by excitation signals output by the motor control main chip and comprise sine analog signals and cosine analog signals; determining a target rotor angle of the rotary transformer according to the output signals of the rotary transformer; determining a motor rotor angle according to the target rotor angle of the rotary transformer; and detecting the position of the motor rotor according to the motor rotor angle. The motor rotor position detection method and device solve the problem in the prior art that the cost is relatively high when the rotary transformer is utilized to detect the position of the permanent magnet synchronous motor rotor, the cost of permanent magnet synchronous motor rotor position detection is lowered, and the motor rotor position detection method and device can be used to detect the position of the permanent magnet synchronous motor rotor.