Eccentricity　and　inclination　are　common　fault　types　in　magnetic　gears,　serving　as　prerequisites　for　the　stable　transmission　of　cycloidal　magnetic　gears　(CyMG)　and　nutation　magnetic　gears　(NMGs).　Eccentricity　and　inclination　alter　the　permeance　of　the　magnetic　gear　air　gap,　leading　to　the　generation　of　complex　harmonic　magnetic　fields　within　it.　To　clarify　the　modulation　effects　of　eccentricity　and　inclination　on　the　air　gap　magnetic　field,　and　address　the　limitation　of　current　2-D　magnetic　field　models,　which　fail　to　calculate　the　3-D　magnetic　field　distribution　caused　by　magnetic　gear　inclination.　This　article　presents　a　3-D　mathematical　model　for　magnetic　gears＇　eccentricity　and　inclination,　termed　the　permeance　coefficient-based　improved　subdomain　method　(PC-ISM).　First,　this　method　computes　the　3-D　magnetic　field　of　the　coaxially　facing　magnetic　gear.　Then,　by　mapping　it　onto　the　3-D　magnetic　field　of　the　nonuniform　air-gap　magnetic　gear　pair　using　the　magnetic　permeance　coefficient,　it　mitigates　the　challenge　of　calculating　the　3-D　magnetic　field　arising　from　eccentricity　and　inclination　while　preserving　accuracy.　The　magnetic　permeance　coefficient　serves　not　only　as　a　3-D　magnetic　field　mapping　for　various　magnetic　gear　setups　but　also　as　a　descriptor　of　the　modulation　effect　of　nonuniform　air　gaps　on　the　magnetic　field.　This　article　examines　the　magnetic　field　characteristics,　including　distribution,　intensity,　and　order,　along　with　the　mechanical　characteristics　such　as　torque,　torque　ripple,　and　axial　force,　and　verifies　these　through　finite　element　simulation.　The　study　found　that　both　CyMG　and　NMG　can　convert　the　th　order　fundamental　magnetic　field　into　the　pm　1　th　order　harmonic　magnetic　field.　Thus,　to　ensure　stable　transmission,　the　number　difference　of　magnetic　pole　pairs　must　be　1.　When　the　minimum　air　gap　is　constant,　the　average　harmonic　magnetic　field　intensity　in　the　nutation　air　gap　exceeds　that　in　the　cycloid　air　gap,　indicating　that　the　nutation　angle　enhances　the　harmonic　magnetic　field　intensity.　In　the　mechanical　characteristics　analysis,　the　maximum　transmission　torque　of　the　NMG　reaches　13.82　Ncdot　$　m,　and　the　calculated　volume　torque　density　equals　189.90　kNm/m3.　At　different　input　speeds,　the　output　speed　of　magnetic　gear　1　(MG1)　quickly　stabilizes,　with　a　transmission　ratio　of　-8.71　after　stabilization.　©　2024　IEEE.