With double circle around shear valvetype magnetorheological damper as the research object, according to the internal selfclosed property of the magnetic field, the magnetic circuit mathematical model was established by using magnetic circuit method. Through the qualitative analysis on the key structural parameters, the structure optimization basis of magnetic induction intensity approximation at piston bench clearance was obtained. Ansoft Maxwell finite element simulation software was used for verification. The results show that the magnetic circuit method is effective and accurate for the initial design and calculation of the doublecoil or even multicoil shear valvetype magnetorheological damper.