Abstract: Disclosed is a low magnetic leakage high voltage transformer in which two winding brackets are mounted in an electrically insulative holder frame to hold two primary windings and two secondary windings at two sides, two U-shaped FERRITE cores are inserted into the winding brackets from two sides and abutted against each other, and a straight FERRITE core is inserted into an insertion slot on the electrically insulative holder frame into contact with the abutted U-shaped FERRITE cores and isolated from the primary windings and the secondary windings by baffle flanges of the electrically insulative holder frame, and two electrically insulative caps are capped on the winding brackets and abutted against two opposite sides of the electrically insulative holder frame to increase the creepage distance between conducting terminals of the windings and the FERRITE cores, for enabling the secondary windings to output two high voltages stably for driving multiple loads.