The utility model discloses a transformer with good sealing performance. Annular transformer comprising an annular transformer body, a hollow groove is formed in the annular transformer body. Whereinan insulating tape is adhered to the surface of the annular transformer body; a left insulating outer frame is mounted on the left side of the surface of the insulating tape; a right insulating outerframe is installed on the right side of the surface of the insulating tape, the right insulating outer frame and the left insulating outer frame are fixed through a first fastening bolt, a whole formed by the right insulating outer frame and the left insulating outer frame is placed at the top end of the base, and a first clamping groove is formed in the top end of the base. The transformer with the good sealing performance has the good sealing performance, normal work of the transformer is not affected, meanwhile, a traditional integrated external electric wire is arranged to be in a detachable connector port form, dismounting and mounting are convenient, time and labor are saved during maintenance, and the maintenance convenience and the practicability of the transformer are improved.