The utility model provides a pair of device and compound the bypass switch that restrain initiative overvoltage, its device that restraines the initiative overvoltage includes: three parallelly connected individual event body, its body includes: two excitation winding on two iron core posts of centre are backward twined to iron core, difference by four iron core posts constitute to and the line side winding of winding in two excitation winding outsides. The device that restraines the initiative overvoltage connects in parallel and has compound the bypass switch, and compound the bypass switchincludes bidirectional thyristor, mechanical switch and reactor, wherein the series branch constituteed of reactor and mechanical switch is parallelly connected with each the individual event body inthe device that restraines the initiative overvoltage with the bidirectional thyristor respectively. The utility model discloses eliminated the generator from the excitation, initiative overvoltage suppressing device can automatic adjustment to suitable reactive compensation capacity to eliminate producing from exciting conditional sum phenomenon, for big unit direct access electric wire netting creation condition.