Abstract: In response to the need for intrinsically atomic oxygen (AO)-resistant polyimide (PI) ultrafine fibrous membranes in space exploration activities, the electrospun intrinsic AO-resistant PI fibrous membranes were prepared by introducing Si and P elements into the PI molecular structure in this paper. The effects of the incorporation of Si and P on chemical structure, micromorphology, optical properties, thermal properties and AO-resistant properties of PI fibrous membranes were systematically studied. The experimental results indicate that the surfaces of obtained PI fibers are continuous and the fibrous membranes are smooth. The glass transition temperatures of all PI fibrous membranes are more than 290 ℃, and they all show good thermal stabilities below 450 ℃. With the addition of Si and P elements, the AO erosion yields of PI ultrafine fibrous membranes are reduced by an order of magnitude compared with Kapton^® after being exposed to AO at a fluence of 2.0×10²¹ atom/cm².