The utility model discloses a prevent isolator mistake and close instrument with adjustable, including bracing piece, staple bolt, insulating extension bar, the top of bracing piece is equipped with the buckle, and the staple bolt is adjustable structure or integral type structure, is provided with the snap ring to the side of the staple bolt, and the buckle is connected with the snap ring cooperation, insulating extension bar and bracing piece threaded connection to according to the nimble length of adjusting the bracing piece of on -the -spot actual need. The utility model discloses simple structure uses in a flexible way, convenient, can examine and repair on -the -spot actual need according to the transformer substation, freely adjusts the length of bracing piece and staple bolt, upperand lower electrically conductive arm through the fixed isolator of mechanical buckle makes things convenient for the change maintenance work of isolator universal joint and bearing, has prevented effectively that the mistake of examining and repairing in -process isolator from closing, has improved the security of transformer substation's maintenance work.