An installing and connecting structure for an automobile pedal support body assembly and a brake main cylinder comprises a pedal bottom plate, a left support body, a right support body, a thermal insulation pad, a pedal reinforcing plate and a brake main cylinder and vacuum booster assembly. The pedal bottom plate is provided with a bolt through hole, a casing pipe is welded in the bolt through hole, the thermal insulation pad is provided with a hole matched with a pushing rod assembly of the brake main cylinder and vacuum booster assembly in size and a hole matched with the casing pipe in size, the casing pipe penetrates through the thermal insulation pad to make contact with the pedal reinforcing plate, and a bolt on the brake main cylinder and vacuum booster assembly penetrates through the pedal reinforcing plate and the casing pipe to be fixedly connected with the pedal bottom plate through a nut. The thermal insulation pad does not need to be provided with a large hole matched with the pedal bottom plate in size, the hole only needs to be matched with the pushing rod assembly of the brake main cylinder and vacuum booster assembly in size, the cutting-off area of the thermal insulation pad is reduced, the excessive noise produced by an engine outside an engine room can be effectively prevented from being transmitted to a cab, and the NVH noise performance inside the cab is improved.