The invention discloses a permanent magnet synchronous motor rotary transformer zero position detection method and device. The method comprises the following steps of: giving an alpha-axis voltage U1and a beta-axis voltage 0, and reading the current absolute position deltathetaa of a permanent magnet synchronous motor through a rotary transformer decoding chip, giving a q-axis voltage U2 and a d-axis voltage 0 and measuring an A-phase current amplitude Is1 after the rotating speed of the permanent magnet synchronous motor is stable, giving a q-axis voltage -U2 and a d-axis voltage 0, and measuring an A-phase current amplitude Is2 after the rotating speed is stable, and enabling the Is1 to be equal to the Is2 through adjusting deltathetab, (deltathetaa+ deltathetab) being the zero positionof the permanent magnet synchronous motor at the time. According to the method, the zero position of the permanent magnet synchronous motor is detected through a phase comparison current amplitude method, a dynamometer rack with high power and a twin trawling motor with high power are not needed, the detection precision is improved, and the cost is reduced.