In oil-paper insulation, the accumulation of space charge distorts the electric field, which can be harmful to the insulation of the dielectric and even lead to breakdown. Under the complex working conditions of different electric field distribution and temperature gradients, the space charge effect of the oil-paper insulation system within oil immersed transformers will be more prominent. Based on the bipolar charge transport model, this paper explores the characteristics of space charge in oil-paper insulation under the influence of various factors by using numerical simulation. Firstly, the space charge distribution in a double-layer oil-paper dielectric was obtained by applying different electric field simulations. Then, the charge distribution patterns of single-layer and double-layer oil-paper insulation under temperature gradients are comparatively analyzed, and the temperature gradient effect of oil-paper insulation was obtained. The results showed that the increased electric field strength in oil-paper insulation promoted the injection and accumulation of homocharge and the presence of interfaces exacerbates the field distortion under constant temperature conditions. Additionally, temperature gradients exacerbated the heterocharge accumulation near the low-temperature side, thus distorting the electric field, and the distortion was more severe for double-layer oil-paper.