The invention discloses a temperature gradient test system of major insulation of transformer winding in case of a blocked oil channel. High and low voltage direct current power supply modules are used for carrying out analog control on load loss of all segments of high and low voltage windings. An insulation rubber block simulation transformer is used for simulating a phenomenon of a blocked oil channel of a transformer. A temperature sensor is used for measuring temperature of all parts of main insulation of windings. Thus, according to the invention, the temperature gradient distribution of the main insulation of the windings of the transformer in case of the blocked oil channel can be researched, thereby facilitating researching of a thermal aging condition of the winding main insulation in case of the blocked oil channel caused by faults of solidification of oil flows, piling of foreign matters in oil and expansion of winding insulation under the natural oil circulation, so the states of insulation performance of the transformation are further ensured.