The utility model discloses an on -line monitoring intelligence voltage transformer, combination sensor sets up in secondary terminal box. The oil tank lower extreme of voltage transformer body is provided with the box, is provided with the terminal block in the box, be situated between damage sensor and protection device, and communication connection is all shielded with the end with the damage sensor that is situated between to combination sensor. Combination sensor decreases sensor and voltage transformer integration setting with being situated between, combination sensor realizes putting the test and being situated between voltage transformer's office decreasing the test with the damage sensor cooperation that is situated between, the combination sensor and damage sensor some as voltage transformer that be situated between, a hardware condition that is to voltage transformer's partial discharge and dielectric loss's live test is provided, thereby play the effect that can conveniently detect partial discharge and dielectric loss at electrified in -process, the live test who makes circuit transformer is convenient, it is safe and accurate, without requiring disconnecting mutual -inductor power, thereby the economic loss owing to having a power failure and bringing has just also been reduced.