A multi-winding inductor comprising: a magnetic core comprising a first cover plate, a second cover plate and four magnetic columns, the first cover plate and the second cover plate being arranged oppositely, the four magnetic columns comprising a first magnetic column, a second magnetic column, a third magnetic column and a fourth magnetic column orderly arranged counterclockwise, and two ends of each of the four magnetic columns being respectively connected to the first cover plate and the second cover plate; a winding assembly comprising at least a first winding and a second winding, each of the first winding and the second winding comprising a first portion, a second portion and a third portion; wherein the first portion and the third portion are connected through the second portion in each of the first winding and the second winding; the first portion of the first winding is arranged between the first magnetic column and the second magnetic column, the third portion of the first winding is arranged between the third magnetic column and the fourth magnetic column, the first portion of the second winding is arranged between the fourth magnetic column and the first magnetic column, and the third portion of the second winding is arranged between the second magnetic column and the third magnetic column, wherein the first portion of the first winding extends to a first surface of the magnetic core and forms a first pin of the multi-winding inductor on the first surface of the magnetic core; the first portion of the second winding extends to the first surface of the magnetic core and forms a third pin of the multi-winding inductor on the first surface of the magnetic core; and wherein each of the first winding and the second winding is a flat wire with a width and a thickness, the thickness is less than the width, wherein a width direction is parallel to an extension direction of the first magnetic column, wherein the first winding and the second winding are crosswise such that the second portion of the first winding and the second portion of the second winding are overlapped. a magnetic core comprising a first cover plate, a second cover plate and four magnetic columns, the first cover plate and the second cover plate being arranged oppositely, the four magnetic columns comprising a first magnetic column, a second magnetic column, a third magnetic column and a fourth magnetic column orderly arranged counterclockwise, and two ends of each of the four magnetic columns being respectively connected to the first cover plate and the second cover plate; a winding assembly comprising at least a first winding and a second winding, each of the first winding and the second winding comprising a first portion, a second portion and a third portion; wherein the first portion and the third portion are connected through the second portion in each of the first winding and the second winding; the first portion of the first winding is arranged between the first magnetic column and the second magnetic column, the third portion of the first winding is arranged between the third magnetic column and the fourth magnetic column, the first portion of the second winding is arranged between the fourth magnetic column and the first magnetic column, and the third portion of the second winding is arranged between the second magnetic column and the third magnetic column, wherein the first portion of the first winding extends to a first surface of the magnetic core and forms a first pin of the multi-winding inductor on the first surface of the magnetic core; the first portion of the second winding extends to the first surface of the magnetic core and forms a third pin of the multi-winding inductor on the first surface of the magnetic core; and wherein each of the first winding and the second winding is a flat wire with a width and a thickness, the thickness is less than the width, wherein a width direction is parallel to an extension direction of the first magnetic column, wherein the first winding and the second winding are crosswise such that the second portion of the first winding and the second portion of the second winding are overlapped.