In the study of the transportation of low energy electrons through insulating capillaries, the experimental results are very different and depending on many conditions. This leads to some controversies on whether the mechanisms of the electron guiding exists or not . This work studies the electron beam with an energy of 1500 eV transmitting through the insulating PET capillaries of 400 nm in diameter. The capillaries have never been irradiated by any beams before. The two-dimensional angular distributions of transmitted electrons and their evolution are measured by a Mirco-channel Plate (MCP) detector with the phosphor screen. The energy distribution of the transmitted electrons is also measured by a mesh system before the MCP detector where the stepping voltages are put on and the transmitted electrons are recorded by the MCP detector accordingly. The experimental results show that the intensity of transmitted electrons increases with the charging time when the capillaries starts to be exposed to the electron beam, and a typical charging-up is observed. During the charging process, the angular distribution width of transmitted electrons increases from small to large, but the center of the angular distribution remains the same. The energy spectrum of the transmitted electrons when they reach the stationary state shows that the most transmitted electrons keep their initial energy. This work provides new experimental evidence for understanding electron transport in insulator micropores, and gives the conditions for the formation of guiding electric field in micropores that may form guiding effect.