The space electric field distribution in oil under impulse voltage is very important for the design of transformer insulation. The existing research only focused on the characteristics of the electric field at a certain point in oil-pressboard insulation structure. To in-depth study of the space electric field distribution in oil under impulse voltage changes with time and space, the measurement platform for the space electric field in oil under impulse voltage was built. The space electric field distribution in transformer oil under lightning impulse voltage was measured, and its changes with time and space were analysed. The results indicate that: As the applied voltage increases, the measured field strength begins to be lower than the applied, and the difference between the maximum measured and applied field strength increase. The space electric field distribution in oil in the wavefront time stage gradually becomes uniform with the increase of time. In the tail time stage, the weakening effect of the space charge on the electric field in oil gradually weakens with the increase of time and the applied field strength is first higher than the measured and then gradually lower than it.