The　accuracy　class　of　optical　current　transformer　(OCT)　is　influenced　by　the　uniformity　of　the　magnetic　field　in　the　magnetic　collecting　ring.　Traditional　finite　element　calculations　and　exhaustive　search　methods　require　extensive　computation　and　are　prone　to　getting　stuck　in　local　optima.　Therefore,　an　OCT　magnetic　field　optimization　method　based　on　the　NRBO-XGBoost　algorithm　is　proposed　in　the　article.　Firstly,　the　ANSYS　Maxwell　finite　element　method　is　used　to　analyze　the　magnetic　field　distribution　in　the　magnetic　collecting　ring,　and　its　influence　on　accuracy　class　of　OCT　is　quantitatively　evaluated.　Secondly,　the　nonlinear　relationship　between　the　magnetic　field　non-uniformity　coefficient　and　the　size　of　the　magnetic　collecting　ring　(such　as　thickness　and　air　gap　length)　is　constructed.　Then,　the　NRBO-XGBoost　algorithm　is　applied　to　optimize　the　magnetic　field　distribution　of　the　magnetic　collecting　ring　by　determining　its　optimal　dimensions.　Finally,　the　simulation　result　of　the　magnetic　field　in　the　magnetic　collecting　ring　shows　that　the　magnetic　field　nonuniformity　coefficient　reaches　0.016,　verifying　the　effectiveness　of　the　NRBO-XGBoost　model.　©　2025　IEEE.