The utility model discloses a big earthed return change over switch based on double acting explosion chamber, double acting explosion chamber on including the support and locating the support, the double acting explosion chamber includes static contact component, be located the moving contact subassembly of static contact component below and the spring operating mechanism that the relative static contact component of drive moving contact subassembly reciprocated, static contact component includes the quiet arc contact, contact seat and locate the shift fork that the drive quiet arc contact on the contact seat reciprocated, the one end of shift fork is rotated with the upper end of quiet arc contact and is connected, the moving contact subassembly is including moving the arc contact, the cover is located the spout that moves arc contact upper end and is reached and move the pull rod that arc contact lower extreme linked firmly, the insulating pull rod coaxial coupling of pull rod and spring operating mechanism, be equipped with drive shift fork pivoted traction lever on the spout. Move the direction removal that arc contact and quiet arc contact can follow relatively simultaneously or carry on the back mutually for the stroke very reduces, and the time contraction of divide -shut brake can also reduce the operating power simultaneously.