The interface of DC accessory insulation and cable insulation suffers both the bulk electric field along cable radial direction and the interfacial electric field along cable axial direction. The distribution and concentration of the two orthogonal electric fields make the interfacial space charge property complex. Aiming at the problem, the cross-linked polyethylene (XLPE) and silicone rubber (SIR) are used to compose a double layer sample to imitate the compound insulation of cable accessory, and the interfacial space charge at XLPE/SIR interface are measured by pulse electro-acoustic (PEA) method under bulk electric field and three different orthogonal electric stresses, namely bulk electric field from electrodes of PEA and interfacial electric field provided by aluminum foil needle-plate electrodes (the polarity of needle electrode is positive/negative) or plate-plate electrodes. Results show that the XLPE/SIR interface space charge changes obviously under orthogonal electric stress (both bulk and interface electric fields). After twenty minutes’ applying of orthogonal electric stress, the interface charge increases first and then decreases with electric stress under the interfacial electric field from negative polarity need-plate electrodes, which leads to an injection of electrons to XLPE from negative electrode; interface charge decreases with electric stress under the interfacial electric field from positive polarity need-plate electrodes, which increases the injection of positive charge to SIR from positive electrode; under the interfacial electric field from plate-plate electrodes, the interfacial space charge decreases a little.