The development and test of China’s first ±525 kV cross-linked polyethylene （XLPE） DC cable are introduced. A type of heteromorphic copper conductor with a section of 3 000 mm² was designed， and a water-blocking tape was chosen as filler material. After calculation， the filling factor of the conductor reached 95.5%. Longitudinally permeability tests on the insulated conductor have proceeded under the condition of 2 MPa hydraulic pressure for 10 d and 1 m water column with thermal cycling for 10 times， the length of permeability was 7.2 m and 0.9 m respectively. Copper wires were twisted as a metallic shield of the ±525 kV XLPE DC cable， among the copper wires， two optical fibers were implanted in to achieve the requirements of communication and thermometry online. A composite waterproof sheath was compounded with aluminum-plastic tape and PE， hence， the outer diameter of cable has been minished 10% compared to corrugated aluminum-sheathed cable in the same voltage and section. To verify its electrical properties， voltage test and partial discharge test under AC 525 kV were carried out， then a whole performance type test was taken in National Center of Testing and inspection for Electric Cable and Wire （TICW） referred to CIGRE TB496—2012 and GB/T 31489.1—2015， including load cycle test， DC withstand voltage test， superimposed impulse test and so on， and the conductor passed all the tests. During the load cycle test， the maximum temperature of the conductor was over 70 ℃， and the temperature gradient in insulation exceeded 30 ℃.