The invention provides a test unit for monitoring an oil-paper insulation state, and is suitable for the fields of transformers and oil-paper insulation monitoring. The test unit comprises a computer, an electrometer and a control bus communication cable; a high voltage DC power source and an ammeter are arranged in the electrometer; one end of the control bus communication cable is connected with a control bus interface of the electrometer, while the other end is connected with an interface of a control bus control card in the computer; a low voltage end interface of the high voltage DC power source and a grounding interface of the electrometer are grounded together; a high voltage end of the high voltage DC power source is connected with a first electrode of a product to be tested through a high voltage wire; a measuring end of the ammeter is connected with a second electrode of the product to be tested; and the test unit is provided with a control panel capable of displaying and storing data and setting parameters. The test unit is simple to operate, has the current detecting rate at least 1sps, can generate rich measurement information, is convenient to analyze and process test results, and has lower cost than foreign test instruments.