The invention provides a withstand voltage test method for a combined electrode, and relates to the field of electric dehydration and desalination of raw oil. The withstand voltage test method for the combined electrode comprises the steps that: step 1, an internal component formed by connecting the combined electrode and a high-voltage connecting box is placed in a transparent operating mode simulation box; step 2, a test power supply is connected with a metal end of the combined electrode in the high-voltage connecting box, and a grounding wire is connected with the high-voltage connecting box; step 3, a medium is poured into the transparent operating mode simulation box until the medium is over the combined electrode; step 4, transformer oil is pour into the high-voltage connecting box; and step 5, the test power supply is powered on, and the voltage of the test power supply is adjusted to carry out the withstand voltage test. The withstand voltage test method for the combined electrode solves the technical problems that the electric dehydration and desalination equipment in the prior art has potential safety hazards.