Abstract: In view of problems that temperature of permanent magnet is too high and easy to fail when disc-type speed-regulation magnetic coupler with high power is running, a magnetic circuit method was used to make theoretical derivation for eddy-current loss of conductor rotor, and finite element software was used to carry out research on steady-state temperature field for permanent magnet of magnetic coupler under condition of high power and high load. The research results show that with increasing of slip, temperature of the permanent magnet of the magnetic coupler increases; with decreasing of air gap distance of the magnetic coupler, the maximum temperature of the permanent magnet gradually rises. When slip of the magnetic coupler is in 180 r/min range, the air gap is no less than 18 mm, temperature of the permanent magnet will remain below 55 ℃,the maximum magnetic energy area and remanence of the permanent magnet are almost unaffected, and the normal and efficient operation of the magnetic coupler can be ensured. When the magnetic coupler is in working state of high power and high load, the air gap distance has a significant influence on the temperature state of the permanent magnet. When the slip is 180 r/min, the air gap is less than 15 mm, the temperature of the permanent magnet would rise sharply. When the air gap is reduced to 3 mm, the maximum temperature of the permanent magnet will reach over 180 ℃, and the magnetic remanence will be close to 20% compared with the room temperature, and the maximum energy product will decrease by about 45%. The research results have a guiding significant meaning for temperature field analysis of the high power magnetic coupler.